Before you go too far down the road of politics and policies, but the biggest lever affecting the economic differences comes down to age.
The EU is aging rapidly. Whereas the US had a minor baby-boom with Millenials - there was no equivalent in the EU. So even without any slowdown in labor productivity or even reduction in QOL, the ratio of people participating in the workforce is much lower in Europe.
The EU is aging rapidly. Whereas the US had a minor baby-boom with Millenials - there was no equivalent in the EU. So even without any slowdown in labor productivity or even reduction in QOL, the ratio of people participating in the workforce is much lower in Europe.