US with no 9/11 -
I agree, a lot less grimdark in the Zeitgeist.
No TSA hassles in the airports. I figure airline service still races for the bottom to cram as many cattle in the tibe as possible, though if fuel prices aren't as goofy, maybe it's not near as bad, OR foreign competitors remind us Americans it still can be a pleasure to fly and worth the extra $100.
As far as pop culture goes, I figure things stay pretty much fat, dumb, and happy.
Reality shows reflect our need for voyeurism on the cheap, keeping up with the one-shot weirdos we would've seen on Jerry Springer.
24 might have gone three seasons or so, but without the visceral need for an ominiscient, ominipotent spook to prevent disaster- I like Kiefer Sutherland as an actor, but those scripts were abysmal. West Wing doesn't become as much of a liberal-wank on what Bush with a brain and heart transplant would do in charge of the White House.
Country music is more about having a good time and singing the blues than waving the flag, nobody loses their sense of humor, and Billy Ray Cyrus gets laughed off the stage. One can only hope!
The Internet was coming no matter what. As download speeds got decent, You Tube was almost inevitable. Social media came up bundling things in a convenient package as more folks got comfortable being online.
Economically, there's a lot of crap going on no matter what happens on 9/11. The dot-bomb recession hits right as Bush takes office. Without the distraction of 9/11 and invading Iraq, I'd expect a much harsher critical eye on Enron, Worldcom, etc. Deregulation becomes nearly impossible to defend with big ripple effects say 2003/4.
Delay, Abramoff, etc get rounded up and hammered sooner.
IDK if that would prevent the housing bubble- different issues in play.
Hurricane Katrina would be a national tragedy still, but with better response (a semicompetent FEMA director with good funding and coordination with federal, military, state and local agencies) and Lousiana and Mississippi National Guard units all being on home turf instead of in Iraq, I think the focus wouldn't be on New Orleans but more on the whole Gulf Coast from Pensacola to Lake Charles.
We might see a Gulf Aid concert or two for fishermen and other coastal communities devastated by the hurricane but nowhere near the sense of outrage OTL.
Maybe (way outside chance) CCC gets revived to help restore coastal wetlands and breakwaters, zoning for beach businesses/housing gets more aggressive, YMMV.