You present two issues: 1) the US is slow to adapt to drone warfare and 2) the US is losing to Iran.

For 1), the US isn't in a hurry because there's no actual threat. The lack of drone warfare capabilities only impacts US action overseas and of the little bipartisan consensus left, one thing is clear: no new wars (Trump's Iran war is seen as betrayal from his own party but it's hard to oppose Dear Leader).

For 2), it's hard to win when you don't know what you're doing or declare victory when you don't know what your goals are. I'm not sure there's even domestic agreement that it's a war.