IMO, I’ve always believed Iran or other terrorist organizations have sleeper cells already in the USA, living and working normal lives who will activate when called to.
Instead of a 9/11 type of attack, I think it would be suicide bombers on buses, public events, etc...basically a whole bunch of smaller terrorist attacks all over the country carried out in rapid order meant to destabilize the country.
The critical parts of the electrical grid are pretty much unprotected, the same qirh water sources. Given some of the recent events, many of the police aren't much interested in getting involved unless they have a formidable force with them, and all the toys.
FBI confirms aniñado training camps in US
https://www.newsbharati.com/Encyc/2018/2/2/FBI-confirms-Jihadi-camps-in-America.html
Tow in Georgia: Commerce and Macon. Possible third in Newton Cty
agree 100%