@PolAmKrakow
After ww2, Truman doctrine focused on halting or at least slowing down spread of communism (mainly spread by Soviet Union and Communist China)
Post 1991, such need was no longer in need and was swiftly exchanged by War on terror.
Now we are sitting in a situation post-corona, where a lot of things that were thought of as unthinkable. Are now very real and present in our lives.
The need for U.S.A to stay in NATO is indeed diminished, cause only reason for U.S.A to have military forces in Europe is for American businesses to be protected from a Russian take over. However, if Europe is focusing on pushing out America in every possible via the E.U. U.S.A will then see those businesses as lost either way, and will have to decide between warring on Europe or leaving it to their own fate in the potential clutches of Russia or China.
If U.S.A will be able to negotiate a deal with Russia and China, it would be to U.S.A's advantage as migration from Europe to U.S.A would then increase if Europe would fall for Russia.
That is if elites and citizens in America won't fear or believe that Russia+China would try and invade Homeland U.S.A.
It would work within next 50 years, but next 200? Who knows.
American presence is likely to diminish from Europe if European conflicts are escalated and increased unnecessarily over time. Especially if it would cost more then benefit.
U.S.A has more of potential allies in South Korea, Japan and Poland. Then France, Germany or Spain
Russia and China knows this and testing the waters for American resolve and plans.