Indeed. The Russians carried out a not so clandestine invasion of Crimea and annexed it. And the weakened west, to include the US, could do nothing to stop them. To the OPs point, I think we are already at a point where US influence is weakening, and this is a good example of what can happen.

The days of the US riding in to stop, for example, Serbian genocide of Muslims is over. I for one mourn the loss.