One of the reasons that so many researchers come to the US, even with our decline in research funding over the last 30 years, is because the US makes available so much God damn funding in comparison to any western world. The reason China is starting to outstrip the US? Because they are starting to surpass the US in funding. The only downside I have heard from Chinese scientists is that you tend to get pigeon holed for the rest of your career into things the state wants/needs
I'm a physicist in academia, and the amount of money we have gotten from DoD branches for things that have no immediate military applications is like 40-60% of our budget YoY. Like for straight fundamental physics research.
Most scientists I know who have gone to Europe have had to go into the private sector. And the famous ones I work with have gotten like blank check $10M offers from max planck and directorships with guaranteed $1m/yr funding, and still turned them down.
From a European perspective, the most noticeable sign of this is the scarcity of postdocs at American universities. Some fields and individual labs are better funded, but on the average, the universities lean heavily on students doing the actual research.
The actual expectation is that after finishing PhD, you take a journeyman position, where you can practice the skills needed in an academic career and gradually gain independence while being mentored by a senior academic. Then, if you were successful, you get a permanent position. The postdoc path fails, as there is no clear path to a permanent position. The assistant professor path fails, because the funding system requires you to become a manager without sufficient experience.
European PhDs vary in duration. The most common system is 3+2+4 years for bachelor's + master's + PhD, which is not that different from the American 4+5 years for bachelor's + PhD. (Those are nominal durations, and actual studies usually take longer.)
In most European countries, a postdoc is a nice enough middle-class job. If you are interested in an academic career after finishing PhD, you have good chances of getting a postdoc position. The real bottleneck comes after the postdoc stage, as faculty positions are scarce in most European universities.
A large percentage of the US DoD research budget is going to researchers outside of academia, for example. This includes a lot of relatively pure research with no immediate military application.
There's plenty of academics doing fundamental research in Europe. But somehow the ball is dropped on turning that research into successful businesses. So eg. uni graduates doing research in EU, then move to US & found a startup there, is sadly a common pattern.
As I understand it, mostly due to funding suppliers (gov, VCs, banks etc) being more risk-averse than in US. Regulation pressure doesn't help either.