Man. It's been a while since I've participated around here, despite lurking since forever.
Either way, with the rumors behind a new XFL looming, this seemed relevant. One of the things I thought about though that was especially inspired by the logo is that the 'edgy' aesthetic of both the league identity and the team identities from the original league would be seriously outdated. But it should still have some kind of unique touch to the identities. That said, one of the things I tried to do is find ways of making the teams a collective (IOW, non-plural) nickname that still projected some sort of extra aggression.
Boston Rebellion (Boston was obviously one of the important locations of the Revolution, with several team names paying homage to that, and the alliteration helps. Plus 'rebellion' definitely fits for the supposed 'upstart' league)
Chicago Untouchables (Echoing the earlier suggestion from another user, while it's again not a non-plural name, it gives a shout-out to Chicago's past without making overt gangster overtures and again just sounds like it's tough and imposing)
Detroit Machine (Oblique reference to the city's car manufacturing, along with a low-key one to Robocop, and again sounds collective while still sounding imposing in a way of something superhuman and insurmountable)
Las Vegas Jokers (Again, couldn't get a non-plural name that seemed fitting, but it comes in with the usual gambling allusion, and while not as 'tough' sounding as the others without referencing a certain comic character, it also gives a sense of unpredictability, a surprise to worry about)
California Los Angeles Aftershock (Aftershock, as others have suggested, definitely fits the theme I'm going with, but feels off with the 'California' name. LA Aftershock has a bit of alliteration that rolls of the tongue better.
New York Empire (Because why not? It sounds better than Emperors, with the obvious allusions and makes the team sound like an imposing dynasty right off the bat)
St. Louis Gatekeepers (Couldn't think of a good non-plural name, but St. Louis is the 'Gateway to the West', and gatekeepers need to be tough to keep out the riff-raff. Just woe unto the incarnations of the team that end up middling, due to the prerequisite jokes that'd inspire)
Texas Stampede (Believe it was another earlier suggestion, but it gives obvious allusion to Texas' cowpoke past and other established teams, while leaving an image of an unstoppable, collective force)