Hard to say. I don't remember what if anything US/UK did in the wake of Livenenko being polonium poisoned. That was treated like a traditional crime. But that was also in a time when it wasn't obvious that Russia was sponsoring a worldwide campaign against Western democracy, so I think the stakes are higher now. Clearly, in Trump's eyes, there's very little Putin could do to upset him. The only way this thing could end honorably is if Trump, his kids, and McConnell and Ryan commit ritual suicide. Since that's unlikely I don't know how we solve this riddle.