On the one hand, I can understand why western Europe's put so much reliance on the US for defense. WW2 ended and the Cold War began - no European country was really quite in a position to properly defend itself from Russia.
And honestly, seeing what the US (and NATO, but a lot of the heavy lifting has been done by the US) has been able to do to Russia by arming Ukraine to the teeth... I'd say Western Europe can look at that and quite comfortably say relying on the US for defense is a pretty sound decision. Russia's only gotten to experience a fraction of first hand experience seeing why the US doesn't provide it's citizens healthcare... and it's made the "might" of the Russian military look a lot less mighty in less than a year.
I think it's pretty mental actually, they've managed to make NATO look like it has a purpose again after the end of the Cold War... and not too long after pretty prominent politicians had publicly questioned the purpose of NATO. And now it's pretty clear if Russia did want to start shit with a NATO country, they'd have to be prepared to get nukes otherwise they'd get humiliated on the battlefield.
I still think it was most evident that Europe needed to do something about its energy dependence on Russia in 2014. Or even before that, when Russia rolled into Georgia. That was really all the evidence needed to show that Russia is a European power that has aims of expansion into the rest of Europe. But rather than actually address that, Europe remained reliant on Russia.
A big problem, for Europe... but really everyone in the world.... is that there's a hell of a lot of issues with any of the big energy producers. None are really ideal to do business with. There's a tradeoff between maintaining dignity, morality, and standing up for "western ideals" and keeping energy affordable.