The United States is providing aid to the Ukraine to fight off Russia. While Russia may not technically be an enemy of the United States at the moment, the two nations aren't on the best of terms. This action can be construed as Musk aiding and abetting the Russians, with whom the United States is having "difficulties" with at the moment. Musk should keep in mind the United States has the power to denaturalize him and revoke his citizenship.
He is literally the person outiside Ukraine who has done the most for Ukraine. Othernations couldnt buy capability that Starlink provides. And they got it for free for months. Starlink was attacked by Russians.
So its ridiculous to claim Musk is some anti-Russian element.
Denaturalizing and revoking citizenship would be the least worst outcome assuming the US government tires of someone providing an enemy nation state material support.
Would he even care? Probably a few dozen other nations would be happy to have him and his wealth. Billionaires like that exist outside the national borders that you and I live in...
And plus, he probably still has South African citizenship?