Since the Cold War ended about 30yrs ago the US has progressively withdrawn troops and bases, leaving just a few operational, all the European defence is shared out through NATO, combined, Russia is outclassed. We have seen Russia has struggle to overwhelm little Ukraine and has probably lost 100,000 troops in the process, thats more than the original men committed to the first invasion force.
Russia has used the threat of nuclear escalation which is its only effective defence, its time to make the decision, either call his bluff, or settle Ukraine now.