Not so long ago the US was made fun off in large parts of the world, maybe it's because of the blond hairs, maybe it's because it distracts attention to something. Maybe it's not so bad to not be in a now 26 countries alliance that couldn't even collectively manage an pandemic, i mean if you are together but do everything separate what's the point other than pretending to form a block... If Russia really wants to invade Ukraine they will do so, the EU is not gonna stop them because they argue to much about what country (sorry member state) should shoot first, the US might fire a few rockets until some republicans unearth Bidens shady son's dealing once again.. most of the world will be angry at Russia do some sanctions for good measure but that's about all.
The same applies to china except for the fact that sanctions will hurt the rest of the world more then it hurts them, hence Trump's attempts top make India more of a production hub then China.
Now we can blame Brexit uk, we can blame the EU or the Us but the groundwork of this is done long before that, we (the world) shouldn't have allowed dictatorships like China to become so powerful. That's the issue.