"Full war economy" is an insane mobilization of all aspects of a county's industrial capability, and if the US were to undertake such an endeavor it would near instantly implode. This is not very unique to the US though, as modern economies are not designed around being mobilized in such a way, and there is absolutely no way to mobilize a country in such a way without causing extreme and lasting damage; which makes it unlikely for the US and its capitalists to do.
The US is also not "running dry", they have given Ukraine a tiny little bit of scrap from their pile of aging weapons that were primed to be scrapped anyways. Whatever the US is giving is quickly replaced by new war material from new contracts from the Military Industrial Complex.
Active US war itself is also incredibly unpopular, which is why even the most bloodthirsty libs immediately shy away from the thought when its brought up. This is also why the US avoids any and all direct conflict, and instead pokes and prods, and engages in proxy wars.
All in all, all of these factors combine to mean that the US simply wants a new proxy war that they can fund and run contracts off of. The possibility of launching an invasion of Iran is minimal, but the US would froth at the possibility to arm Israel if they decide to launch an attack.
They just want to sell guns, loans, and contracts. War profiteering.