Well, it's not necessarily an easy question to answer. Looking it up, capitalism is generally defined as private ownership of the means of production, like SonGokuMonkey said (probably best to disregard my definition of it, then). But he believes that the economy is far too regulated by the government, whereas I believe it's regulated too little
. Nonetheless, I think it's widely agreed by most economists that the American economy is, at the end of the day, very free market.
Also, free market capitalism seems to be defined as a kind
of capitalism, so there's that.