Not yet mentioned is that this is the first time the US is actively working against their allies, and it's not just the Europeans.
If - or when? - the US leaves NATO, the EU will finally have a big incentive to buy local. Right now the EU buys most of their arms from the US. Germany's 100 billion Euro special fund created at the beginning of the war in Ukraine mostly went to US purchases.
It's a Chinese article but I found it pretty good (I'm German by the way): https://english.news.cn/europe/20240913/04cbc80f51674bd7b0a2...
Here in Europe the sudden change with regards to Russia, and how they treated an ally that the US spent at least the last two decades actively building up (Ukraine military would have been quickly overrun in 2022 without all the work and support the US provided), there now is fear that when we really need it the US may do what they did with the Ukrainians.
It may not even be political, but it's no longer far-fetched to imagine that the US will demand major concessions and payback in order to resume support, ignoring any previous agreements, just because they can.
What still works in favor of the US is, at least here in Germany, our politicians. Just now, what did the new government - consisting of the two same old major parties that have ruled all the time since this country was created - concentrate on? Major fundamental changes? No! Immediately they went for useless spending for some of their clientele, and they only went for "borrowing a lot of money" instead of institutional changes. They may be concerned, but in the end they still refuse to move. Even the new trillion is again just a new special fund kind of setup instead of fundamental changes, and you can bet most of it will disappear in the major inefficiencies of our systems.
They have also always had a lot of problems creating a true alliance of European arms manufacturers, each country pushes their own interests with little regard for the rest.
However, should they finally wake up at least a little bit from their long fat slumber, many billions of reliable purchases from the US could disappear - plus the European arms makers will become much more competitive internationally too. Especially if more countries have doubts about the reliability of relying on the US for ongoing long-term support. That could be bad for the US arms industry from two fronts.
BY the way, I am much more mad at the Europeans, my own German government(s) especially, than at Trump. We did nothing for two decades, watching Russia prepare for war. To me it also makes perfect sense for the much more populous EU to deal with its own problems without having to ask a far away country. It's kind of like "regression towards the mean", no? The US only came to Europe because of some truly special events, but at least since the fall of the East Bloc there really is no reason. We were lucky because of all the momentum, it took the US a while to realize this (and some really bad wars). I consider the developments good for Europe in the end. We are forced to confront reality.
I just wish the Ukrainians would not have to pay such an enormous price for all those fuck-ups. Which includes a lot of actions to get Ukraine into NATO at some point (see https://en.wikipedia.org/wiki/Ukraine%E2%80%93NATO_relations) - and now when they really need it, and also because of all of that, the rug is pulled from under them.
With the world watching, that too may be a factor for future US arms deals.
In addition, the world and Europe especially also depend on the US when it comes to software. The OS and Office 365 are ubiquitous. For the cloud we have alternatives and one could use those, it is much much harder for a business not to use US software.
If Europe becomes more self-reliant, we may see some movement here. It would not work bottom-up, but all the EU has to do is demand things at least for the public sector, piece by piece. This could create some certainty and cash-flow to create European software, and create a wide basis on which businesses could later build upon.
For the US, leaving Europe has a few risks. What is never mentioned are all those secondary effects of their NATO support and dominance: This way the US keeps a lid on too much European independence, and goes far beyond defense. If Trump and Musk think it's a no-brainer to give that up, well, as a European I support them. If we can't do anything with such a chance it's our own fault. This could be really good for Europe.