SHIELD is UN sanctioned, but the thing about Maria Hill is that the U.S. pushed for her, as other countries did, to distance SHIELD from Fury. Not to say that SHIELD is a U.S. lapdog in Civil War, but remember Tieri's Weapon X? He had Wolverine ask Fury why SHIELD won't step into Weapon X and Fury tells him that Weapon X has the President's favour and SHIELD can't touch them.
Kind of still thinking Guardian will show up in either Civil War #5 or the next Civil War: Frontline, or the one after the next Frontline. Maybe Omega Flight might show up in one of those three issues, somehow, but that's a stretch. Guardian and Talisman as AF reps is more likely.