S-400 can be resolved if we see their positive moves on selling patriot and taking us back into F-35.It has to pass the senate with 2/3 majority for the President to not be able to veto it.
But even if it passes we'll see what's going to happen. Biden has already had dealings with Turkey as VP, and he's come a few times to apologise, maybe he understands how bad the entire situation has turned into, but he'll know we won't back down and sanction will just make things even worse.
Just deploy those to Libya transfer to UMH, problem is solved.