According to Karl Marx's list of ten things needed to become a communist country the U.S has applied-in one form or another- nine of them.
"America" is not a country, it's a continent formed by three sub-continents (north, central and south america).
Now about the question, since it's about the USA... Marx's wrote his works more than 100 years ago, with Germany in mind (the fact that Russia was the place where the revolution took place and was successful is still a high topic among historians) --by then, the USA was an underdeveloped country, without a big proletarian base or an industrial/urban developed production system, which was the requested condition for the revolution (again, Russia was a contradiction to this request). Therefore, you cannot apply Marx's theory 'directly' to a country today. The capitalist system has developed internal restraints and "decompressing" mechanisms that ensure that, even when the inequality and the poverty or the income distribution are ignominious, the system is not under danger of disruption.
Capitalism, as Marx said, might have the seed of self destruction, but it also has self-preservation mechanisms (corporations, NGOs, formal democracy --even in non-democratic countries--). Also, it offers what some people might call a 'messianic' or 'religious' promise: the best of the worlds is here, on earth and while you are alive, and you need money and success to attain it (I am talking about the protestant capitalism, not the catholic one, which came later): therefore, the success of capitalism is guaranteed by the fact that the lower classes want to become middle class, and middle class wants to become high class. This ensures all of them, especially the middle class, is ultra-conservative, fighting to keep the status-quo, so they can (someday) be high-class and enjoy what the system promises (of course, the status-quo needs to be based on inequality, so you have classes and people fight to escalate in the social chain).
what do I know?...