>US could get much more if they would be allies since technically there are no obstacles
It's weird, it's almost like pioneering and supplying technology (VBIED's) to kill American troops, and founding terrorist organizations to kill American allies somehow sours the relationships between the two countries.
by no means are they some altruistic peace lovers, but considering other countries in the region, US could get much more if they would be allies since technically there are no obstacles (apart from 1979 US embassy issue, but nobody got killed, all released eventually... worse things happen, ie Behgazi and nobody cares if it serves some agenda).
If you go there nowadays, all the signs are in 2 languages - Farsi and English. Everybody speaks at least a bit English. Compared to say France :)