Securing your own position is contingent on having a proper deterrence to US invasion or belligerence. Unless you are thinking of appeasing them, but I doubt that European defense minds would consider that.
I doubt they'd adopt outright appeasement, but they would be walking very cautiously.
I do not know what kind of mental gymnastics you make when you say NATO doesn't support the war in Ukraine, but it actually does - with the NATO SG going to Ukraine in a show of support.
AFAIK, there is no precedent to what will happen if a NATO country attacks another NATO country - we came close to that when the Turks and the Greeks almost started fighting a few years back.