Wait for the ricochet
Presumably Snowden's money - or the bulk of it - is in Russia. It's where he "earned" it - and yes, I acknowledge that not everyone will agree that "earned" is the appropriate word. It's where he lives, and the money wouldn't be any use to him elsewhere.
I also assume that there is no regular forced transfer of money from criminals in Russia to the USA. (In the UK, we have a subtle way of doing this - we let them buy mansions and football clubs and the like in the UK, and so we get their money that way.)
Anyway, if the US lawyers find out a way to get Snowden's money transferred to the USA, then this would presumably open the doors for other similar activities.
Such as further subpoenas in the US, to reveal who else has profited greatly from dealings with Russia. Or, if the Russians are annoyed, they might just reveal details of the Russian dodgy dealings of US citizens.
Are you listening, Mr President?