I think the United States uses an economic model other than capitalist or interventionist. If one were to coin a descriptive word, it would probably be "corruptionalist," in which government uses tax policies and taxpayer dollars (subsidies, grants, etc.) to create competitive advantages for those that dole out the largest campaign contributions.
We've created a system where instead of having to bribe each individual in Congress, all you have to do is bribe the two parties and then they use soft money to keep the rank-and-file in line.
It's this corruption of the capitalist model more than the model itself that has caused the economic turmoil we now find ourselves embroiled in.
History has shown that the best system is one in which government defines the rules within which business operates and then leaves businesses alone as long as they stay within those rules.
Those rules should promote the nation's general welfare and should take into account that while competition is far better than regulation, in the absence of true competition, you'd better have regulation.
Regulation within the economy should be temporary, though the true goal being to restore rather than to replace a competitive environment.