The USA doesn’t seem to want to quit the NATO. However, they are fed up with financing the lion’s share of the alliance.
The Pentagon’s ultimatum to the rest of the NATO says: Either you start spending more money on defense or we start reconsidering our participation in the alliance.
It’s not accidental that the United States want to see their Western allies spend more on their dense programs. That’s a fair deal. Every member should contribute to the alliance once they have joined it. Why should the USA sponsor the NATO? This is the rhetoric coming from the Pentagon.
The current relations between the United States and the rest of the NATO result from Donald Trump’s attitude to the alliance. He thinks that the NATO is an outdated military alliance and needs to be improved at best.
Just in case you don’t know, every NATO member should spend at least 2% of their GDP. However, most of the 28 NATO members do not stick to this requirement and keep spending less than that, maybe hoping that the USA and other stronger economies will cover the gap for them. While this could have been the case during Obama’s administration, Donald Trump is not determined to let it slide anymore.
NATO Map

The whole point is, Donald Trump doesn’t reject the NATO. He just wants it to be stronger and more efficient than now. And this is only possible if all of the members start contributing to this goal.