EU has done really well on passing big laws such as GDPR in the recent years, while the US can’t even seem to decide whether to fund their own government. Why do you think Europe is doing better than the US? One would think that since EU is more diverse it would be harder to find common ground. And there were examples of that during the Greece debt crisis. But not anymore, it seems.
Aside from the multi party systems, i’d say another important reason is that EU countries tend to have a political spectrum.
The US has a far right party with LGBT rights and weed and a reactionary fascist party. But actually progressive or even a lot of conservative positions are not represented in politics at all. Even Obama was against general health insurance, which is a system most conservatives in the EU value.
So the space of political positions even on the table is much smaller and there is no need to compromise, as for instance neither US party opposes total surveillance of the citizens and the idea that doing any form of business with a company does not grant it the total ownership of that persons privacy just doesnt exist in the political debate.
I guess multi party systems and having a political spectrum go well hand in hand. A party in a multi party environment cannot entrench against “the other”, at least not all of them. It must stay open for negotiations if they want to be part of a coalition forming a government. Since these compositions may change based on how the people vote, parties need principally be able to talk and govern with all other parties, to get anything of their own agenda done.
On paper this sounds like a recipe for “nothing gets done”, since power is fractured so much. So I’m still wondering. It’s a great question. Also a loaded question, which isn’t that easy to quantify.