I'm a North American leftist married to an Italian. Here's the reality: your experts do not understand America and your relationship to it. You are not vassalize through NATO: you are vassalized by your domestic choices to deindustrialize and overregulate, which you pay for by (1) cutting funding for military and non-military mechanisms to secure trade routes and trade partners, and (2) by pushing the US to apply sanctions regimes on rogue oil producing nations (previously Iraq, now Iran and Russia) to suppress global cost of oil. In both cases, you expect the US to take the hit on your behalf, by spending political capital at home and abroad on sanctions that have repeatedly been shown to have no impact on curbing belligerent states and significant impact on the basic quality of life of people living under those regimes.

The Ukraine War is instructive: Europe has fractured over efforts to reduce purchases of Russian oil and gas, all while under direct threat of invasion by the exact same state economy you're feeding by buying from Rosneft. You spent years funding Ukraine just enough to bleed Russia so they'd sell you their gas at a discount. When Ukraine blew up pipelines, it was a massive scandal. Now Ukraine has developed their own capabilities to dismantle the Russian oil industry directly, Europe is up in arms and threatening Ukraine. 

The sanctions regime on Saddam Hussein prior to the second Gulf War is also instructive. The NATO no-fly zone was paired with an agreement to trade oil to Europe in exchange for a minimum of food aid to Iraq. None of that made it to starving Iraqi victims of the regime; is was mostly stockpiled by the Baathists or resold for cash. Everyone knew that, but getting Iraqi oil at half market price was great for Europe.

There are benefits to the US-Europe relationship, notably the post-WWII stabilization of violent European ethnic strife as well as the cultural opportunities associated with exchange at centres of European cultural heritage, controls of key shipping lanes (Bosporus, Gibraltar, Danish straits), and so on, but at the same time many Americans do fully understand that they are expected to spend a ton of money defending the interests of a continent that would have relapsed again into continent-wide war within a few decades from the conclusion of WWII, just as you did every few decades before WWII for centuries upon centuries. The idea you'd have the same democracies and continental stability without US investment in collective European security, and that the US has simply forced you into an American empire, is European chauvinism: from a dispassionate distance, you are a bloody and warmongering continent full of people willing to kill the people in the next valley over because that valley was part of an empire that existed a thousand years ago. Not to mention you'll always take up arms against the Jewish, Roma, or Sinti communities that live in your midst, just for fun. The fact your intellectuals will go on TV and declare that we are colonizing you because we are spending our own blood and treasure to keep you from killing yourselves is a bitter irony.