I also find it pretty hard to believe that either US or European countries would defend other European countries. If they didn't respect the Budapest memorandum, why would they respect NATO Article 5 when it would mean actual attacks against their people, potentially nuclear attacks?
As a reminder: France, US and UK, and others, signed a series of treaties referred to as the "Budapest Memorandum" (there's like 7 slightly different ones) that generally promised that if Ukraine (explicitly including Crimea), was attacked, with Russia specifically called out, all other nations would
1) formally declare war on Russia
2) start conventional open hostilities on Russian forces to defend Ukrainian territorial integrity
Russia obviously violated the treaty in 2014. This should have triggered those responses ... it didn't.
Needless to say, no one actually upheld the treaty. As for US presidents, Obama didn't, Trump didn't, Biden didn't and now Trump is also not doing that. In Europe, Hollande didn't. Macron didn't. In the UK ... and so on and so forth. A full list would be very, very long, and include a LOT of governments and parties from all across the political spectrum.
Therefore I find the premise of this article to be flawed. Essentially all western countries (including all powers in Europe: UK, France, Germany) chose to mostly ignore their obligations toward Ukraine in international treaties, for more than a decade now. Trump is doing something bad, and so now we blame it all on Trump? I mean, the guy sucks, but, he's the cause of this problem. If one is extremely generous one might even say he's trying to solve it, and (for now) all he's done wrong is alienate/insult US allies' governments. And the Ukranian government. But this crisis is not of his making.
Frankly, Poland, NATO or no, is in the same boat. So are the Baltic states (MAYBE they can count on Poland), but ...
Ukraine, Poland and Germany are all countries that would be extremely hard to physically prevent from acquiring both nuclear weapons and delivery systems. There's Ukranium mines near Kyiv, they have nuclear power plants and knowhow, including heavy-water breeder reactors. They have rocket expertise, and in fact could use Russian/USSR rocket designs.