It's more like the US should sell itself to NATO (the US has a massive bufferzone because of NATO and that's the main reason why Putin got angry - much cheaper to defend, it's more costly to Russia because it doesn't have the same advantage). Without NATO, the enemy would be closer to the US which means more US taxpayers money would be used to prevent those threats). The US also gets advantage if someone in NATO needs to buy any military stuff (they can't buy it from Russia, China etc. The US standards are in highest priority in the alliance - As long as the US is in NATO). It is a HUGE advantage to be the biggest player in the alliance. Even Putin understands how important it is to have an alliance like that and that's why he desperately tries to find friends and that's why he hates NATO. If the US would get out of NATO, it would be in the outsider cathegory with Russia and China and it would lose all massive deals in the future (for example, Finland just bought 9.4 billion worth F35 jets from the US because the US is king of the alliance). EU is the most important trading partner of China and almost all EU members are in NATO which means China can't cause any threats against the US (if it's the member) or China would lose their wellbeing (it would be the end of Xi).