the usf has access to light vehicles . their is no excuse for it to completely fuck up your early game.
most usf and soviet players however completely overextend themselves and have not learned to be defensive while you pump out the adequate counters.
The earliest USF light vehicle would probably still be the WC51, at 1 CP. You're already way behind at this point. Outside of the pretty meh at the moment Mechanized doctrine, their earliest light vehicle is the M20, which runs a total of 70 fuel to get (teching+vehicle cost). That's about 5 minutes in if you actually managed to hold your fuel point.
Allies (especially USF) being defensive in the early game is a loss. USF doesn't have a super unit that can come out and turn the game around in the late game. If you don't win the early game as USF you're going to lose unless your opponent makes gigantic mistakes.