It's a big piece of it, seemingly.
The US has an interesting constitution:
- First past the post. Such systems tend to favour fewer parties. The UK (also FPTP) barely has more than two parties. In most of continental western europe, there's considerably more, due to proportional representation. On the continent you end up having a bunch of different opinions, and you don't have to squish every issue onto a liberal/conservative axis. For instance you get socially conservative big state parties. Or socially liberal big state parties. Or socially liberal small state. And there's other axes too.
- A separate executive. In the UK even though they have FPTP, they have a government formed by the leader of one of the parties, and they "whip" the MPs to vote according to the party line, subject to various forms of sanction depending on how important an issue is. In the US, you choose two legislatures and a separate president. If they're not in agreement, it de facto entrenches the existing status quo by making it hard to change the law.