I think airpower wise, we would absolutely destroy them. If an assault rifle can take out a Ceph Gunship, an A-10C Warthog would decimate it in under a second. It would destroy any alien ship for that matter, save for maybe the Warrior (which is no longer a problem, thank Nomad). Ice pellets cannot kill jet aircraft flying at Mach 2, nor can they fire a missile at something 10 miles away.
On the ground? Depends. Urban combat, we can't match them. They are too strong and too fast to kill with anything designed for urban combat. Out in the open however, we could take them on if tank crews were skilled enough, and sniper teams with gauss rifles could take them out from 1000 yards.
Naval warfare, no. Crysis proved this. We would be swarmed with more ships then a Phalanx could handle, and everyone on board would be killed.