Americans, and people living in American colonies, also have first-hand experience with American imperialism. I'm not sure why you think your experience trounces theirs?
Because "communism" is both an economic and a political ideology, while "capitalism" is only an economic one.
And before the nitpicking starts, I'm well aware that monied interests can influence democratic politics. That does not make an economic system a political system. It would be like calling democracy an economic system.