This is one of those actions that is completely understandable and an unambiguously moral decision, but the blowback has the potential to upened the entire post-WW2 American centric global financial order. Maybe for the better, maybe for the worse, I don't know, but it'll probably depend alot on what your vantage point is.

The US would be shooting itself in the foot.

Do you like being the global economic superpower with hegemonic influence over the world economy? Because this is a good fucking way to get other nations to tell you and the World Bank to fuck right off. Can't seize assets that are not part of your banking regime, and this definitely incentivizes de-dollarization.

Why only Russian Assets? There are probably a few $Trillion assets in tax-shelters within America's own borders. Charities, Churches and Foundations, and that's before you even get to shell companies and holding companies.

More then enough money to pay for literally anything, including paying down the federal deficit if you don't understand monetary policy and you feel like that is important for some reason.