I’m no military expert by any means but US appears to be obsessed with destroying some super important target to win, like they did with killing Iran leaders only to find out that new leader replace the perished. The same with the other stuff, they have super important radar and super important ships that need to be defended and a failure creates irreplaceable loses. Iran on the other hand, just like with their super…
This is the same problem that doomed us in Vietnam, in Korea, in Iraq, and will doom us in Iran. It's also the same problem that fucked over South Africa and Rhodesia and seems to be a common problem for white supremacists, but that's just my editorializing.
In any case, showing up and killing shitloads of people and then leaving does not win wars, it just LOOKS kinda like it does if you have no idea how to win wars, and assures you promotions in your organization. As soon as your military leadership starts citing that instead of actual progress on the conflict and the objectives at hand, it's a safe bet they are on their way to loss via attrition.
And that's not the ONLY factor of course, our military is too expensive and relies too much on fancy tech as opposed to solid strategy, everything we use is hideously expensive so any losses we take tend to hit harder, etc. But I think this is the most important thing to cite when discussing America's inability to actually wage war in a way that does anything besides get service people killed and enrich the MIC.