The US backs NATO purely out of self-interest. As much as I detest the actions of Russia and laugh at their propaganda around Nazis in Ukraine, biological weapon mosquitos and the like, some of the points about US hegemony are right on the nose and this fact has been clearly evident for a long time.
Intervention in WW2 was delayed repeatedly and done on terms to create the biggest advantage possible to the US in establishing US hegemony. It's interesting how countries such as Israel are gifted the resources they ask for, yet countries that were literally fighting for survival were given crippling repayment terms in exchange for assistance. The difference was that those countries were competitive with the US at the time and crippling them economically was beneficial to the US.
The USSR prevailing in Europe would have been catastrophic for US hegemony and so the US did what it had to do, setting up infrastructure to prevent it from happening. The USSR at the time couldn't have been held back with cast-off weapons and so this wasn't the approach. European states, still suffering from WW2, became beholden to the US as they couldn't afford to defend themselves at the time, much of it due to the onerous costs arising from US intervention in WW2.
Now look at the situation in Ukraine, the weapons exist to ensure Ukraine wins but the cast-offs are being used because Russia is comparatively weak when compared to the USSR in the day. It's more advantageous to the US that Ukraine doesn't win quickly because more of Russia's military strength can be sapped this way, at the expense of the Ukrainian people, so cast-offs are sent that are good enough to hold the line but not good enough to go on the attack. As soon as Ukraine start to make some progress militarily the resources from the US dry up and the almost stalemate situation returns.
So when has NATO Article 5 been activated? Once, in defence of the world's largest military against a rag-tag militia. The act they committed, while deplorable, pales into insignificance compared to the acts being committed based on US funding in Palestine and compared to the acts being committed based on the lack of US funding in Ukraine. Whilst responding to the attack was so urgent that it required the invocation of Article 5, they still had time to go into Iraq for some oil first, because you always have to be looking after that self-interest.
The US is not a white knight coming to the rescue, any assistance should be viewed as a trojan horse for US self-interest and interference. We need to be able to properly stand on our own feet and stop depending on US resources in Europe for defence. Just because it is there doesn't mean it will always be there, and being able to make use of those resources when you need to generally comes at a terrible price.
No doubt, Russia, China and others are more malign influences in the world, but is being less malign than Russia the benchmark for who you get into bed with now?