Agree that evidence is appropriate, but as someone that's not in the US (NZ), we do broadly see it that way. US politics is very pervasive internationally, and you guys definitely appear to be split way more into 'left' and 'right' (as one example).
Compared to NZ's politics... which is more like a blob of parties which sit pretty close the centre, and sometimes parts of the blobs move more left or more right.
But naturally the dichotomy comment doesn't hold true in all circumstances.
Multi-party systems generally tend to have less of a gap between parties. Especially if no single party is strong enough to hold majority power alone in a parliamentary system, decision-making requires collaboration between multiple parties.
A lot of the polarisation in US politics is probably due to the two-party system. I don't know whether or not that has anything to do with people thinking in false dichotomies in other contexts.
There really seems to be some dteong cultural tendency to do this.