To be fair, the US defense expenditure is for all of US defense including domestic, and our military interests outside of Europe.
NATO is primarily a European defense organization. If we account only for our European defense spending, it would be a lot closer to what the European nations are spending on their own defense.
The US current defense expenditure is about 2.8% of GDP. France is about 1.8% and Germany is about 1.4%. The UK is about 1.9%. You could argue that US forces anywhere in the world could be deployed to Europe in defense of NATO countries if war broke out, but most likely we would not abandon our military support for Asian countries,
I am not going to defend NATO, I think it is obsolete and should be dissolved at some point in the future as we improve relations with Russia.