> why would the US concede?
Because it has no way of achieving its objectives.
I don't think that has stopped anything so far, but I appreciate your optimism.
More accurate to say that the US is not willing to pay the price to achieve its objectives I think (depending on who/when you’re asking what exactly the objectives are of course).
The US has mostly achieved their objectives (as best as I can tell - the strategy isn't exactly coherent) - Iran has much less missiles, and much less ability to produce them.