Why exactly would Iran hope for the US to be a one-party autocracy full of imperialists who won’t suffer non-whites or non-Christians?
A lot of things.
For one thing, Trump / Project 2025 wants to kill NATO. Trump has already sown enough distrust that Germany is looking to secure military independence from the US.
Another thing is Trump and his companion ideologues are manipulable, as per his relations with Putin, Kim Jong Un and the Sauds. Even if they can’t turn him against Israel, they can certainly goad him into making brash decisions.
Then there’s the matter that the MAGA Republican Party favors loyalty over principle, which scares away its own intelligentsia, and creates a brain drain. We already see the Project 2025 plan to replace government department staff (who have education and experience) with Trump and MAGA ideology loyalists (who do not), which is going to speed the regime’s plummet into corruption and decadence.
The latter 20th century was defined by the US being the baddest dog on the field, tempered only by the USSR being right there to harrow the US and keep it busy. Now the cold war is ended, the US has just turned into a military bully for the interests of its own oligarchs. (It doesn’t help that the white Christian nationalist movement has been pushing the US towards fascist one-party autocracy since the FDR’s New Deal, as explained in Behind the Bastards two parter How the Rich Ate Christianity ).
Genuinely free, fair states are a threat to autocrats, far more than other autocrats, so seeing the US fall to one-party autocracy is absolutely on Iran’s holiday wishlist.
They may get it too, depending on if Trump wins the election, or his coup d’etat is successful, or civil war breaks out in the States.