I think it might be so effective because the whole political spectrum in the US is ultimately projected onto two parties (and their presidential candidates). I am not a political scientist but if the US democracy were more pluralist in terms of the number of political parties, then it would perhaps be harder to manipulate voters using the "civil war" messaging.

Because Israel (Netanyahu), or France (Le Pen), Italy (Berlusconi), Germany (Weidel), England (Johnson) weren't using civil war messaging?

This seems pretty global.

> civil war messaging?

I'm very certain every political party likes to pretend every election is a civil war.

Very odd selection you've chosen there.

I was referring to external influences in democracies with few parties, like the US and the UK.