First, its important to have a context. Words like "fascism" are thrown around in the capitalist media in ill responsible ways without anyone providing a clear definition. This opens the door to this widespread confusion. Fascism should be seen as a system where the state rules over people through terror. Where people have no rights and/or voices. Where this repression of rights is facilitated by the state. In fascist societies people who dare rise up against even the most non-confrontational whims of the state are viciously attacked, arrested, tortured, and murdered. This is a reality where nothing happens that isn't sanctioned by the state, regardless of how inhumane the position and/or actions are.
For most people in the U.S. the classic example of a fascist regime is of course Nazi Germany. The rise of the Third Reich, or the Nazi Party, came about in Germany in 1933 with the rise to power of Adolph Hitler. Under Hitler, Germany went on to basically attack the entire world in an effort to impose its political hegemony. In the course of their brutality, the Nazis consolidated their support among the German masses by promoting the concept that Germans were a higher breed of human beings. The Nazis appealed to the frustrations of the German people. Germany, for the last 100 years, has boasted the highest percentage of college educated persons than any other country so that drop of elitism was already there and the fact Germans saw themselves as suffering and repressed from the results of World War I, which like World War II was fought in large part to suppress Germany's political dominance aspirations, helped create the conditions where this appeal of German exceptionalism was able to germinate. Hitler wrote extensively in his autobiography "Mein Kamph" that power is achieved by properly utilizing propaganda as a tool to control the thinking of the masses of people. For the Third Reich, propaganda meant using fear as a tool to push the German population, already uneasy about its unstable position, to focus on certain segments of their populations as the source of their difficulties. It was the "Southern Strategy" on steroids. Invoke fear against other powerless people to stimulate support for a bourgeoisie nationalism based on insecurity and ignorance. The traumatic results where approximately 12 million people being systemically murdered by the Third Reich, including about six million Jewish people. A side note is the Jews were always in Germany and all the other European countries because Ashkenazi Jews are European people. As this genocide took place, the benevolence of the great U.S. didn't even see the need to get involved directly in the war against the Third Reich until eight full years after Hitler was in power. Its that late effort, almost after Hitler had successfully consolidated Germany's power over an entire portion of the world, that these modern day so-called fascists point to to connect their alleged anti-fascism with the U.S. role in World War II.
The problem is there can be no connection between the U.S. and anti-fascism in any real world analysis. Its true that the U.S. did not become the most powerful country in the world until the the rest of the capitalist world had exhausted its resources and suffered overwhelming losses in the the war effort against Germany in the 40s. Its also true that the U.S. did not have colonies in Africa and the rest of the world. Those who defend U.S. imperialism point to those two realities often in defending U.S. hegemony. What those unfortunate souls never mention is the U.S. didn't have colonies, but they supported all of the European powers who did and that support helped ensure the exploitation the colonies facilitated stayed in tact. The U.S. was an unquestioned ally for Belgium and its merciless role in dominating the Congo. That region of Central Africa is of course the most mineral rich region on Earth. Without Congolese rare Earth minerals, you could not be reading this right now. Belgium's terrorism in controlling the Congo led to King Leopold's massacre in Congo at the turn of the 20th century where between 10 million and twenty million Africans were murdered by Belgium's King. Although this genocide is equal in numerical devastation as Nazi Germany, far less people know about it. The point here is that the U.S. wasn't at the table at the Berlin Conference in 1884 that divided up Africa for Europe, but as the U.S.'s power grew, its capitalist leadership understood that its interests stood in unity with those carried out by the European colonizers. So, yes, the U.S. supported Belgium. It supported France, Britain, Spain, and all the colonial powers in their efforts to terrorize, control, and dominate Africa and the rest of the world.
And, as the U.S. emerged as the dominant world power after World War II, it settled into its role as chief beneficiary of colonial efforts in Africa. U.S. corporations understood that they needed cheap African mineral resources to be profitable so it was consistent with the corrupt values of capitalism for the U.S. to assume this role. So, to recap that piece, colonization results in the theft of cheap human and material resources which fuels capitalism. The fact so many capitalist corporations profit from destabilization in Africa this has to mean this country has openly supported the subjugation of Africa for decades. Today, the U.S. has taken over the dominant role in subjugating Africa. Its corporations are all over Africa and the U.S. military is also all over Africa to protect those interests. There isn't a single destabilization happening in Africa today that isn't connected to this unholy relationship. Whether its issues in East Africa e.g. Ethiopia, Somalia, or Sudan, or Southern Africa, etc, this is true. The fallout from all of this is millions of Africans murdered. Millions more displaced. Africa being in a continued state of destabilization. Every openly fascist regime in Africa the U.S. has supported. The apartheid system in Azania (South Africa) which was just overturned in 1994, would never have been able to hold on as long as it did without unlimited U.S. political, economic, and military support. And this is the system that personified fascism e.g. the apartheid system was based on racist segregation as legal policy. The framers of the apartheid system always credited the U.S. colonization of the Indigenous people in this country as inspiration for their fascist system. The Mobutu regime in the Congo was delicately created largely through the U.S. (through its destabilizing of the National Congolese Movement and the assassination of its leader Patrice Lumumba) from 1964 through 1997 until the people were able to finally run Mobutu out of power. Mobutu's regime with its mass killings, disappearances of opponents, and quashing of any dissent, is the poster child of fascism and Mobutu probably couldn't have lasted one month without extensive U.S. political, economic, and military support. There are many more examples from the U.S. support for the brutal Conte regime in Guinea, support for Central Intelligence Agency trained Kagame in Rwanda, on and on.
For any sane person, these facts make it impossible to reconcile fascism with any support for the U.S. No one reading this can give a logical explanation for how the U.S. holds any moral superiority over Nazi Germany. In our minds the only difference is the U.S. has advanced the techniques around using fear to control the masses that were so effectively utilized by Nazi Germany. Still, the exceptionalism that fueled German support for the oppression of so many is the same exceptionalism and reactionary nationalism that fuels U.S. support for oppression against humanity that so many people within this country so conveniently ignore and dismiss exactly the same way Germans did during the holocaust.
The final statement here is that if you consider yourself an "American" you cannot be an anti-fascist. Even the existence of the U.S. is the result of the murderous theft of Indigenous people's lands so even the concept of such a thing as an "American" is a nod in support of fascism. If you consider yourself an American, or you support any element of the U.S. empire continuing to exist, you cannot be anti-fascist. You are very much a part of the fascist team, right along with the neo-Nazis, KKK, etc. In some ways you are worse because at least that type of scum is honest. The proper correction of this confusion is a complete renouncement of the U.S. and clear statements that you are a person of the world committed to justice for all of humanity and you cannot be that if you are an "American." The same nationalism that Hitler used is the same nationalism that defines "American." Make your decision, but regardless of whether you choose right or not, you should know that us colonized people see right through you.