There is definitely truth that Europe has relied on US defense for too long, but what the US got in return is hard to put into words and economic terms. We bought your tech, culture, defense and so much other stuff.

This rift won't close anytime soon

https://www.youtube.com/watch?v=uXdtafGdIVM

Once all the Germans were warlike and mean,

But that couldn't happen again.

We taught them a lesson in 1918

And they've hardly bothered us since then.

If that were true they wouldn't have wasted enormous amounts of expensive ammunition in Iran.

Additionally a number of countries have "unfair" advantages over others. There are 2 straits that control access to the oceans. Which means Denmark and Norway control free trade routes (land routes are not "free" as in they are taxed) into Germany, Sweden, Finland, the Baltics, and of course Russia. This can't be fixed, and the UK effectively occupies Gibraltar to prevent it.

Spain (I'd say Spain and Morocco, but really ... Spain) controls sea access for all Mediterranean countries, from Italy to Georgia, Algeria to Greece. France (and Morocco) being the major exceptions to this. This can't be fixed, and is currently blocked by what is effectively an international force. Spain is not happy with this.

Turkey controls (and intends to tax) trade routes into all the black sea countries, which is most of Eastern Europe.

Oh and UK and the Netherlands, for reasons that are slightly less obvious, control free trade into Belgium.

In addition to this, most countries do not have the resources they need. Not even to survive. And even most countries that could be self-sufficient, aren't (cough Germany, really, WHY????). Really only France is somewhat close to self-sufficient. Specialization, on a country level, is a necessity in Europe, most countries do not have access to free trade routes and are utterly dependent on trade, in other words: they have to pay to survive.

Essentially the situation is simple: all European countries, except France. Spain, UK and Portugal (and, yes, Ireland) COULD get themselves into a secure position, but haven't (and so if it came to it, it would be very hard to do in a short time). All other countries probably can't do it at all. So all these countries have good reason to attack each other.

So the question with getting Europe's armies weapons is: the natural situation is that they'll try to destabilize Europe rather than stabilize it, because that is in most countries' direct economic interest. Historically, they ... you can say Europe was more peaceful than places like the areas of the ottoman empire, for example. But that should not be confused with peaceful in an absolute sense. In fact, the last 80 years or so have been remarkably peaceful, with America guaranteeing access to international trade. Well, I'm sure Russia would counter "guarantee access? You mean control access", and yes, that's been done.

Unfortunately it's very clear that America's power, especially measured relative to other countries, is waning. Meaning America is still far more powerful than, say, Turkey. But it used to be easily 100x more powerful. Now ... it looks more like 10x. Opposing Turkey will be a huge effort for the US, far more than the Iran war will be. US's deal, the Pax Americana, was that America would simply guarantee free trade routes with it's military for everyone, in fact, that's what the Iran war is really about (free trade for everyone behind Hormuz). In exchange, US gets the dollar. Many nations, most obviously Iran, but Turkey, Indonesia, China, Somalia, ... have all taken steps to tax the trade routes they control, which will over time create an untenable trade situation for a very large number of countries.

The situation for Germany in the long term is a simple choice: they can either pay, or attack. We all know what their historical choice has been, as soon as you have a somewhat prolonged economic crisis. Germany is not alone in this, in fact all of Eastern Europe is more or less in the same situation. A decent chunk of those countries are arming themselves (for example, Germany, Poland, Ukraine, and Finland have all given hints they're building a nuclear force)

The problem with America weakening is that the US wants free trade, because that directly benefits the US greatly, whereas most other factions want to control trade instead. Turkey, Iran, China, Indonesia, even Spain's current government if we're honest and others want to (go back to) taxing other countries. Historically they have succeeded at this, but it resulted in constant wars.