I remain hard-pressed to argue that the animated series takes place today, aka the third gulf war.
My indication for this is their MOLLE Gear, which has been issued in the new millenium, and their weapons, Botasky fielding a M14 EBR with various attachments, and Packy using a KAC-47, which was a weapon developed by Knights Armament for special forces, specifically to be an AR-15 like platform, which uses AK-47 magazines and subsequently itīs ammo.
Both guns are relatively new and have not been around in the second gulf war...