If down the road US becomes so anti-science.
I think this is just people getting worked up tbh. The only thing we have any reason to "fear" is NASAs money being moved from Earth Sciences to spaceflight, which is bad for climate change research but not obviously bad for "science". Furthermore the US remains (and will for the foreseeable future) remain at the top for both University research due to its plethora of excellent research Colleges, and private company research, due to its, uh, robust patent laws.
On the other hand, China remains a place where no one except the Chinese want to do research, owing the questionable ownership over the results and the fact that espionage and, and, basically, thievery have such a large role in their large scientific projects.
Finally, I see little reason to think that, were research to flood out of the US for some unmentioned reason, it wouldn't end up going to Europe. Europe has a large population of English speakers, it's open to outwards investment, has a bunch of world class research institutions and universities as well as a bunch of multi-national cutting edge projects like CERN, the ESA.
I don't think the US will cease to be the world's largest progenitor of research any time soon but if it were, I'm sure it would be Europe that succeeded it.