wrt to Transnistria .......that would be a silly move by putin .....but them he has made several silly moves from the invasion onwards resulting in NATO expansion , reinvigorating of NATO and the expulsion of russia from most of European trade
widening the conflict beyond Ukraine would be a red light for Europe and the US - I imagine an immediate result would be US declaring a state of emnergency .......this then allows Biden to bypass congress and give as much aid as he likes to Ukraine this would also polarise the US voters and make it much harder for trump to be elected Europe would also become galvanised and even more determined and the voters of their countries would understand the need for military aid to oppose rusisan aggresssion