I do not believe America is truly polarized, in the sense of a widening ideological gap between the left and the right. It only seems like we are because of tribalism and a vocal minority.

Most people have political affiliations, and may feel strongly about it, but are actually politically moderate when you get down to the issues. Not that they are necessarily ideologically moderate, though I'd still say the majority of people are.

Most of the people that are pointed out as extremists are (in my eyes) really only crusaders for one or two particular issues, like say trade or immigration, and not just hardline left or right wingers.

America may be a two party system, but we have just as many voting blocs as any other country. (If not more than average) Neocons, the many flavors of alt-right, paleocons, evangelicals, the tea party, the LCR, constitutionalists, libertarians, wallstreeters, moderates... and that's just the GOP.

Not to say that there aren't extremists, that's undeniable, but I do not believe that people are getting more extreme. If anything I'd say that those voting blocs I mentioned earlier are the ones that are drifting apart. People aren't becoming more politically extreme, necessarily, I'd say they're becoming more ideologically diverse and politically distinct.

Honestly, I'd be surprised if either party lasts much longer in their current state. People are becoming increasingly dissatisfied with the two party system, the two parties themselves, and the political deadlock that comes with them.

The problem is that people perceive factions within parties drifting apart in terms of becoming more/less conservative or liberal when they're just differently conservative/liberal.

In other words, they're thinking two-dimensionally. Without depth.