No, it really isn't. The rest of eastern Europe's countries remember what it was like to live under the Russian thumb and they have plenty of modern weapons and well-trained soldiers salivating to ensure Russia is going to be a crippled husk for the next few generations. Western Europe is none to fond of Russia either. And if America stops helping because an obvious Russian puppet president has taken power, that's only going to make it worse.

America may be the sole "superpower", but bear in mind that that means Russia is not a "superpower". They're a peer to the various countries of Europe at best, and by this point I would not even call them that. Ukraine has more tanks than Russia does now. America's already done a lot of the heavy lifting in breaking Russia, if they bowed out now it's not like everything resets to the way it was in 2021. Russia is still on the ropes.