I actually wasn't aware there were a large number of dedicated US rock arrangers. Seems like it takes forever to find one on OCR (which I rarely go to to begin with) and like I alluded to, Ailsean's the most noted one by basically everyone.
Yeah, there are quite a few of them around. You'd be more likely to find their stuff on VGMix if it were up for a number of reasons than on OCR. Here're some songs and remixers to check out (at least ones I like, anyway):
BrainCells is sick. Make sure to get both of his remixes from OCR. He had a bunch of stuff on VGMix too, but that's not going to be up again for a while. He has a collab with CarboHydroM called Dual Storm that you can snag from CHM's site. And speaking of which...
His cover of the Space Harrier theme, Limitless Skies, is nifty. I also really like his Ikaruga covers, Antimatter and Saber Bird.
From Within is my favorite track from him; it's a rather liberal cover of the mines theme from DKC2. His remix for the Kirby's Adventure project, Free Breezin', is neat stuff too. <3 Butter Building.
Definitely La Hora es Tarde, the Clockwork arrange Smeg mentioned. I'm a fan of Light In the Fortress as well. Check out his videos too.
Prozax doesn't come out with new songs very often, but they're killer when he does. He and Midee put up excellent collabs in Kick My Axe, Tactile Freefall, and The Twelfth Commandment.
Ryan did two killer covers of Follin tracks for DoD, Catacombs Beneath the Twilight and The Fuzz Scuffle.
That's probably good for now.