Here is a list of Allied units in Red Alert 2.
Infantry
GI
GIs, also known as Government Issues, are the main allied infantry unit. GIs have fewer hitpoints than Conscripts but a much higher rate of fire when deployed in sandbags. Deploying also increases a GI's range.
Engineer
Allied engineers are functionally identical to their Soviet counterparts. Engineers cost $500 and are capable of capturing most enemy buildings and repairing friendly buildings. Engineers can also be used to capture tech buildings and repair civilian buildings. Engineers are totally defenseless.
Attack dog
Allied attack dogs are identical to Soviet attack dogs except in appearance. Attack dogs cost $200 and can instantly kill any ground infantry unit. Attack dogs can also automatically sniff out spies, revealing them.
Rocketeer
Rocketeers are fast flying infantry units. Rocketeers are very vulnerable to anti-air fire. They may be useful for scouting or killing isolated enemy infantry, or in conjunction with a spy disabling the enemy's base defenses.
Navy SEALs are allied special forces capable of rapidly killing enemy infantry and using C4 charges to detonate enemy buildings. They are amphibious. SEALs are vulnerable to vehicles and base defenses.
Chrono Legionnaire
Chrono Legionnaires are expensive units which teleport around the map and target a single enemy unit or structure, slowly erasing them from existence. During this process, the enemy can move or be harmed, and the Legionnaire is vulnerable. Once promoted to Elite, Legionnaires become much quicker and more effective.
Spy
Spies are noncombat infantry units capable of disguising themselves as enemy infantry. They will not be automatically attacked by most units and base defenses while disguised. However, they can still be manually targeted by players and guard dogs will reveal their disguise.
Tanya
Tanya is an allied special commando who can rapidly kill enemy infantry and detonate enemy buildings. Tanya is amphibious, allowing her to appear where she is not expected. Tanya is effectively a slightly upgraded navy SEAL.
Vehicles
Grizzly Battle tank
Basic allied tank that has more speed but less firepower and armor than the Rhino tank.