It doesn’t work that way, each country spends it for themselves, NATO allows to combine the defense force.
The reason US spends so much is to maintain its status of super power and to allow us to live without having wars on its territory. For example what happened in Ukraine in 2014 and in 2022 is sobering experience that if you are militarily weak others will exploit the situation.
A lot of things that we are assuming are normal are possible because of it. For example. US naval force for example allowed to protect international waters allowing for global trade.