My guess is that, while the U.S. military cannot topple the regime, we can do enough real damage to Iran's military capacity and their industrial infrastructure that elements in the Iranian armed forces will overthrow the mullahs. I am assuming that our Air Force and Navy are far superior to anything the Iranians have, which is largely their own plus imports from China and Russia. Russian arms have always been inferior to Western arms, going back to the Cold War era. The Russians have struggled against largely Western armed Ukrainians. The Chinese military equipment quality is questionable. During the Twelve Days War, it did not do very well against Israeli and American attacks on Iranian nuclear sites.
If my assumptions are correct, President Trump is playing for an Iranian backdown, despite their apparent intransigence.