Most of the smallarms on the ground are 5.56mm's. There are some .308 rifles being issued. These are mainly sniper rifles. The SEAL teams will sometimes deploy on a mission with 7.62mm rifles.
The main militaries in N. America and Europe still deploying large numbers of 7.62mmNATO battle rifles in general issue are Mexico, Norway, Greece, Portugal, and Turkey. All of these nations issue variations of the HK G3.
The M60 has pretty much been replaced in many units with the M240, which is the US designation for the FN MAG.
The M241 is the predominant squad auto on the ground. The US has found that a mix of 5.56mm and 7.62mm SAW's is a good combo.
As for the Marines, they have stated that they want to make sure that each Marine rifleman is issued the M4 instead of the M16A2. They have developed the squad designated marksman concept where one man in a squad isn't carrying the M4, but an accuratized M16A4 flattop with an optic.
The most powerful weapon at the disposal of US troops on the ground is a radio and a map to call in fire missions.