I suppose in theory the US could just starve Roscosmos of funding by cutting back on implicit subsidies. That would require having a contingency in place to kee

I suppose in theory the US could just starve Roscosmos of funding by cutting back on implicit subsidies. That would require having a contingency in place to keep the station viable without Russian involvement. The problem is that would be massively expensive. As you say, that’s a third of the station. In practice you’re quite right, that plan is completely unviable.