This was not an alliance action, but individual European countries making the decisions that best suited them. That cannot be criticized, but this does not constitute an alliance. NATO is obsolete if it defines its responsibility primarily to repel a Russian invasion, especially since it refused to create a military force capable of doing that. It is obsolete in that its original mission is gone. It is obsolete in that it regards the U.S. as the guarantor of Europe’s security, when Europe is quite capable of incurring the cost of self-defense. If European nations are free to follow their own interests, then so is the United States.
When we step back from the argument between the U.S. and Europe on NATO, we see a broader reality. First, the European Union is fragmenting and that fragmentation necessarily affects NATO. Europe is in no position to undertake unanimously supported NATO operations. Nor is it in a position to incur the political costs of a massive military buildup. For the Europeans, NATO is important because it guarantees that, in the extraordinary circumstance of a European war, the U.S. is, under treaty, required to be there.
The United States has other interests. It is interested in preventing Russian hegemony over the European Peninsula, but the U.S. can effectively address that by placing limited forces in the Baltics, Poland and Romania. Just as the Europeans have devolved NATO into bilateral relations between the U.S. and each NATO member, the United States can do the same. Similarly, the U.S. can accept the status quo in Ukraine, written or unwritten. Kiev has a pro-Western government, the east is a de facto autonomous region, and the rights of ethnic Russians in Sevastopol are guaranteed by the Russians. The U.S. is not going to war in Ukraine, and Russia is not going to war there, either.