Quick trip down memory lane:
9/11: committed by Al-Qaeda, with pretty much all being Sunni Arabs
Al-Qaeda: transnational Sunni extremists that have committed terror and operate all over the globe in Africa, Asia, w.e.
ISIS: Sunni extremists opposed and fought by Iranian backed militias
Al-Nusra Front: Sunni extremists opposed and fought by Iranian backed militias
I can keep going but you get the point. You look at the last 20-25 years and Sunni Islamists drawing from Wahhabism have perpetrated overwhelming majority of terrorism. They are they ones throwing gays off rooftops, force women in Hijabs and so on. Even basic familiarity with history and you see that Iran's Shia's haven't overlapped with these groups and historically have been at war with them through proxies. I don't care to white wash the IRGC because i'm sure they also have probably perpetrated barbaric things, but many of the gulf Arabs that have put serious money in spreading Wahhabism/muslim brotherhood are objectively worse. The Arabs are framed as our greatest allies in the middle east, while the other side is the number one sponsor of terrorism. At least try to look past some of the propaganda framing.
Hamas is Sunni and is supported by Iran, they care more about fighting America and Israel than they do about their religious differences. But you have a lot of Shi'ite terrorist groups too(all funded by Iran). Hezbollah, AAH, Houthis, Al ashtar, etc.
Sunni terrorist groups have been the largest generally, but right now there is no country funding, arming and protecting terrorists at anywhere near the level of Iran. The fact that these terrorists disagree with those terrorists isn't an argument anyway. Burn them all