Command & Conquer: Generals - Zero Hour/USA

USA Structures

 * Fire Base - The Firebase is basically a fixed long-range cannon, which can be garrisoned by four infantry for added security.


 * Detention Center - The DC has been removed from the game entirely. Its intelligence capabilities now are available at the Strategy Center.

Infantry
Chemical Suits is now available from the Strategy Center, offering all USA infantry increased resistance to toxins and radiation.

Vehicles

 * Sentry Drone - The odd little Sentry Drone is intelligence in a can. Immune to anthrax and radiation, this quick robot can detect stealthed units, and becomes invisible itself when totally still. The Sentry Drone is a rare sight online because it adds virtually nothing in combat. It is also the only existing vehicle that cannot run infantry over. With a $1000 upgrade, all Sentry Drones are given 10mm guns, which allow them to act appropriately when hero-hunting.
 * Avenger - The expensive Avenger serves three purposes. Firstly, it rapidly neutralizes incoming enemy missiles. Secondly, it increases the rate-of-fire of all units attacking a certain target. Finally, it brings down enemy aircraft in a deadly lightshow. It can perform all three of these tasks at once, and is therefore very useful in a large firefight.
 * Microwave Tank - The Microwave beam emitted by this unit kills the infantry garrisoned in civilian buildings and temporarily disables all player-built structures. The infantry units within disabled structures are, in turn, disabled. The Microwave Tank will automatically damage any enemy infantry in the area.
 * Ambulance - The Ambulance not only heals nearby infantry, but now repairs nearby vehicles. (with the exception of aircraft)

Air Force

 * Stealth Bomber - The Stealth Bomber can now be upgraded with Bunker Busters, which kill the infantry within ANY structure, even dozer-built ones. If used on a Tunnel Network, the Bunker Buster kills all infantry inside and forces all vehicles to evacuate.
 * Countermeasures - This $1000 upgrade makes allows all USA aircraft except Chinooks and the new Combat Chinook to defend themselves from missile-based attacks with periodic flare-drops, including the planes called in by support powers, improving their survivability during bombing runs.