Maybe, I think a bigger reason is that Europe doesn't have near the level of regulatory harmonization that the US has. There are tons of policy areas where member states just do whatever they want, in pretty important areas. Like the US has a single bankruptcy code, and state commercial codes are all pretty close to the UCC, that's not the case in Europe.
The current EU commission president is pushing pretty hard to create more harmonization to make it easier for companies and investors to operate across Europe.
The Nature Index, which shows that data, already only selects the most impactful journals. I wasn't able to find any data that weighs output by citation count.
The current EU commission president is pushing pretty hard to create more harmonization to make it easier for companies and investors to operate across Europe.