According to this video, I don't think pop punk would really be replaced. The '90s punk scene was inevitably leading up to a pop mainstreaming in the '00s. But that itself would inevitable hit critical mass saturation, and as the video chronicles (around the 10:30 mark), by 2004 or so the aged out fans would move on to either hardcore/metal/indie (if they were thorough fans) or rap/pop (if they were normies). And also the kids would just head towards emo. I don't think any of these scenes were really political at all, which means they'd be largely insulated by the cultural effects of the War on Terror. Which brings me to another video-
There was some pro-war jingoist revenge music like Toby Keith during Iraq, the one antiwar act was the Dixie Chicks and they got absolutely cancelled from history, other mildly critical artists (Madonna, Jewel, the Black-Eyed Peas) were either tepid or quickly self-censoring, the
Rock Against Bush album was full of obscure unknowns, there was System of a Down but I'd personally just argue they were just the '00s Rage Against the Machine which might be a revolving position, some other major artists did turn out anti-Bush singles were out of the Top 40 mainstream (and often kinda sucked), except for Green Day's
American Idiot (at 22:53).
According to this video,
American Idiot was like the one major influential antiwar work of art, and then Bush got reelected in 2004 (~29 min. mark), and then there was just a Kate McKinnon doing a cringey overwrought Leonard Cohen impression on SNL in 2016 type deflation in art, and its replacement by resigned defeat counterrevolutionary art like "Waiting on the World for Change" by John Mayer.
Basically the main thesis of the song is that contrary to that meme before 2016, tough times don't always produce great art. So despite the sweeping changes that the War on Terror and the war in Iraq specifically produced in America... there wasn't that much music made in response to it.
So I guess I would just say not much might change on this front, unless someone wants to attempt a counter-narrative, but these are sure some informative videos!