Why yes, they do care.
They may not care about Afghanistan but they do care about the Central Asian region. It's never about Taliban or ISIS or Al Qaeda. Those are just the lubricants for the thrust of the US Military into the region.
It's about influence.
With Iran ramping up it's nuclear efforts, I reckon US will find another bottle of lube lying around by 2026 or later. Israelis will also find an incredible boost in ME if Iran is knocked out of the equation in Gaza, West Bank and Lebanon. Egypt already pledged neutrality for Sinai after Yom Kippur War and Jordan has always been reluctant to fight Israel. Let's not even think Syria factors in. (I mention this because the Jewish lobby in America is very strong, deeply entrenched and fkin badass.)
Lots of factors at play here but if US can take Iran, it'll have a very strong influence in the Central Asian region, notwithstanding the decay in economy.
There are cooler heads in Saudi Arabia than in Iran in the establishment, that's the level of radicalisation among the authorities.
Civilians are liberal but the authority is a stark contrast in Iran. It's rather unimaginable for MBS to order a nuke on another nation but (Won't consider Raisi because he's rather new) Khomeini totally would've nuked someone if he could.
No one wants a 9th nuclear nation. Especially an Islamic one.