The Ahwazi Arabs (Sunni, coincidentally) are stripped of nearly all basic human rights, enclosed in their own state essentially within Iran's borders [1]. Even the Shia in Saudi Arabia are treated better than how Iran handles the Ahwaz region.
Further, Iran loves fighting wars by proxy for some reason. Hezbollah and the Revolutionary Guard are roaming around Syria like they own it. Hezbollah's hold on Lebanese politics is undeniable. And of course, the funding of Houthis in Yemen who hilariously failed to execute an easy coup, the result of which started a full-blown war.
The region is in turmoil, and both sides are at fault. I personally believe that the US is entirely aware of the troubled sectarian relations in the region, and is using that as a way to get cheap oil and sell arms, which is a valid strategy.
This has to stop. The only lasting solution is dialogue.