In a match up like AFG vs USA, you want to take both of your supply docks and go for a standard strategy. There is no impetus for you to drop your opponent early on unless it's going to be a barracks oriented build order.
Getting around to his supplies and keeping him in his base ought to be your main intentions, this can be easily achieved by skirting back and forth in and out of his base, never engaging an unsafe scenario until you've got the army for it.
In the meantime, you can work on taking your oil and getting your Strategy Center. Keep Missile Defenders around for Laser Locking any of his Vees that come around to harass, they're important for making a solid defense against harassment.
If you plan on being an opportunist, you can take your third supply to boom your economy whilst engaging him around his side of the map, which is what should be happening, because if he's on your side, it means the early game didn't go your way, in which case, you should focus on trying to get him back to his base with harassment of your own.
Overall, the safest thing for you to do with this match up against players on your level would be two supply three barracks, spamming loads of MD's & Rangers to drop at his base and defend your own.
![[RANK] [NMC] Gorge Drought](/community/replaysystem/games_files/2/maps/gorge_drought.jpg "[RANK] [NMC] Gorge Drought")
