It's true that Europe and Canada need to invest more in defense, but the balance is currently 755 billion USD (US) vs. 430 billion USD (EU) [1]. So it's certainly not like the MAGA rhetoric pretends. The US has the benefit of being a large nuclear power, but for a long time the US preferred being the nuclear protector to avoid too much proliferation on the continent.
Another annoying part of the 'they gotta pay up' Trump/MAGA discourse is that it's starting to sound like a mob wanting protection money. This is not how the NATO agreement works. Countries have to spend 2% of their GDP on defense, but it's not a payment to the US. They could buy Saab Grippens if they wanted to.
[1] https://www.nato.int/nato_static_fl2014/assets/pdf/2024/6/pd...