It entirely depends on what you mean. We've had a functioning libertarian party for a while, they've gotten far enough to get on the ballots in a couple presidential races and libertarian candidates have won local elections. We've had fairly strong socialist parties before the red scare era.

Now the libertarians kind of sucks shit, so maybe they're a bad barometer to go off of? Maybe a super populist party would take off in a decade or two, maybe it would just flounder with the same success of the libertarian party. Part of the problem is that political opinions in the US are largely formed around binaries associated with either party, so while a new party might form, it would probably get chucked into a "left" or "right" bucket and flounder in obscurity like the green party.