China has one proletarian party. The US has two bourgeois parties. One might think the ideal would be to have one bourgeois party, and one proletarian party, but that hasn't seemed to work out anywhere.
The two parties couldn't be more different today. Republicans are basically an authoritarian party that would be more at home in a place like Russia - or China - today.
That being said, democracies are about generating consensus between factions with otherwise irreconcilable differences.
There should be overlap on many fronts - that's kind of a feature, not a bug - at least in many cases.