Well of course America if it's modern day Russia, it's no contest. Once the USSR broke up they became substantially weaker.
Now, if you want to talk Cold War era Soviet Union like any time from 1945-1990 I wouldn't know. It would definitely be a very close fight during that era. They had so many nukes and about double their current population back then meaning they would probably have had more troops than us.
p.s. Lenin and communism ftw!!! It's a good idea it just hasn't been perfected when put into practice. But then again capitalism has some great upsides too.