America is not fighting a war of national survival on a limited budget. It's fighting some wars of choice and maintaining a defence procurement industry on a seemingly unlimited budget. There is no way even the total failure of the war will personally affect the people doing the producement, and there is no need for them to economise because they can't run out of other people's money.
So, everyone involved is free to have endless meetings. Senior management can commission studies at great expense then ignore the result on a whim. They can engage in turf wars and internal empire building; after all, the real enemy is the people you're competing with for promotions.
The procurements that have been successful are mostly those resulting from urgent operational requirements, when losing to insurgents with a tiny budget became embarrassing.
(The UK is not immune to this; we've built an aircraft carrier that's supposed to use the F-35, which may not be available and we can't really afford)