The NATO treaty doesn't imply in his wording any obligation for a military reaction to an invasion of a member of NATO. There's no penalty to just respond with a strongly worded letter, but there's an expectation an ally will react militarly.
Will your allies trust you any longer if you just follow the letter of the treaty? I don't think they will. More critically, nor will anyone else.
The US have historically positioned themselves as "defenders of democracy" and have multiple times used that positioning actively. It's inevitable for an expectation to be there for them to do just that. The US is free to violate expectations and just follow the letter of the treaties it has, it is a sovereign nation after all, but the surprised and frankly childish "we have no obligation!" reaction to the blowback is more unreasonable than the expectations for its support of Ukraine, particularly in how it has been handled politically.
Will your allies trust you any longer if you just follow the letter of the treaty? I don't think they will. More critically, nor will anyone else.
The US have historically positioned themselves as "defenders of democracy" and have multiple times used that positioning actively. It's inevitable for an expectation to be there for them to do just that. The US is free to violate expectations and just follow the letter of the treaties it has, it is a sovereign nation after all, but the surprised and frankly childish "we have no obligation!" reaction to the blowback is more unreasonable than the expectations for its support of Ukraine, particularly in how it has been handled politically.