The United States Army functions as the heralds of American power and might in Southeast Asia. From their bases in Japan and the Philippines, the United States Army endeavours to keep Asia safe from the Red menace that has recently appeared in Vietnam in the name of freedom, equality, fair play and the American way.
As a newcomer to the global affairs stage, the United States could be a potential winner. With greater migration and an innovative "can-do" spirit which has caught on even with their European cousins, the ability of America to expand through demographics and political influence cannot be underestimated. In battles, the Americans' ability to capture and hold cities means that they are extremely useful at what Age of Darkness is about: conquest.
And what a war machine you have! America not only has a well-diversified military roster, but it also has faster-building aircraft, with an accuracy and range advantage for Mechanisation-level bombers and onward, as well as free and farther-shooting artillery pieces. Equally, the USA also enjoys slashed ramp prices for all unique light and medium vehicles, so that means cheaper artillery and armoured cars for all so long as you have oil. Additionally, the USA specialises in one special area, and that is the taking of cities. Since conquered cities assimilate faster than any other faction, your will thus find it most expedient perhaps to use your superior forces and artillery advantage to take cities. This is only made easier with your relatively larger repertoire of airplanes and tanks in the early game. One of the main benefits of the American faction is that it enjoys a lower cost to creating citizens, which means that when the time comes to repopulate newly claimed territory, the American player can do this at little or no cost.
Which leaves us to ask one question: what's the catch?
Sadly, there is indeed a catch and it's in the quality and ease of research for most US units, especially vehicles. Although the quality of American shipping can't be sniffed at, the same can't be said of most US vehicles, tanks especially. Firstly, tanks and other vehicles don't enjoy any special perks — they don't have the intel-savviness of the Brits, nor do they have the awesome hitting power of the Russian or German tanks. Tanks are also the Achilles heel of the US as well especially in the early game where their research and upgrade costs tend to be astronomical, but over time become the cheapest in the game.
The American player will discover that economics will be a tough field to master, having only the ability to obtain a higher population count at lower the cost — against many European factions and even China and Japan, the US player will discover it has no special resource accumulation abilities; against the Chinese, he suffers again from having a slower albeit cheaper population growth rate.
Thus a major theme in American strategies is choosing either to rush early, or to boom later on, because turtling — unlike Britain, Russia or Poland — simply isn't a viable strategy. For this reason American strategy depends on geography — vast maps like the Outback and Amazon require an aggressive approach, where the US of A uses its initial resources (better artillery and tanks) to seize cities from enemies whereso possible; if there is water, then it can sit back and take a more leisurely approach towards late game booming, using its superior air force to back up its navy on the high seas, whilst gathering resources to build up its land army. The cheaper cost of US artillery and armoured cars should be taken advantage of, as it would also mean that you can deploy many of these units in tandem with a combined-arms approach to warfare. Use quicker-producing aircraft to strafe tanks and anti-aircraft units, so that your weaker tanks and your numerically superior automobile fleet can then close in for the kill.
(note that many of these units are shared with other nations)
- Rifle infantry: GI Specialists [4-6]
- Recoilless gun: Bazooka M1  => Bazooka M20 
- Machine gun: M2 Browning [3-6] (can be used against tanks and armoured vehicles)
- Conscript: National Guard
- Super-unit: Marine Infantry - SMG squad?
- Flamethrower infantry (only for balance)
- Commando: Rangers. Commandos are armed with rifles.
- Light tanks: FT-17^  => M1 "Combat Car"  => M3 Stuart#  => M24 Chaffee 
- Medium tanks: M2 [3, consumed by M3 Stuart], M3 Lee#  => M4 Sherman# [5-6]
- Heavy tanks: Mk VIII Liberty^ [1, phased out later to M3 Lee] => Pershing 
- SPGs: M8  => M7 Priest  => M40 Long Tom 
- Tank destoryer: M18 Hellcat
- Rocket launcher: Sherman Calliope
- Cannon: Schneider [1-3] => M114 light howitzer
- AT gun => QF 6 lber [6, with Capitalism]
- White Armored Car  => M3 Armoured Car[2-3] => M8 Greyhound# 
- M3 Calliope (requires an M3 chassis, and another tech in order to be created)
- M3 Satan => M4 Zippo
- SPAD => Quadmont AA Halftrack (supplies troops, has offensive capabilities) 
- Fighters: Biplane [1-2] => Mohawk  (consumed by Warhawk) => Mustang 
- Bombers: Caudron R11 [1-2] => B-23 Dragon [3-4] => B17 Flying Fortress [5-6]
- Light bomber: Glenn Martin Bomber  (consumed by B-23 Dragon), Warhawk [4-5] => P-38 Lightning 
- Capital ship: Iowa-class battleship - Average-strength battleship. Capable of outranging warships like the Vittorio Veneto class, but still fragile against other ships, especially such as Bismarck-class or Yamato-class warships. It however is distinguished from other factions by having a lower pop cost, and a fast build time. Theoretically, the USA can churn out quite a number of these warships.
- Battle cruiser: Baltimore-class cruiser - America doesn't build cruisers, it just upgrades its battle cruisers to heavy cruisers. The Baltimore-class heavy cruiser is an upgrade of the battle cruiser - slightly more expensive than the destroyer, but easier to build and has the following benefits: it's as fast an manoeuvreable as any cruiser, but has enough firepower and hull strength approximating the battle cruiser.
- Aircraft carrier: Yorktown-class - the best carrier in the whole game, with a good operational range.
- PT Boat: faster than Coast Guard, has an attack bonus against shorebound infantry.
- Start with Suffrage researched.
- Receive 2 free light artillery unit(s) whenever you build a new Siege Factory or Factory.
- Artillery units upgrade for free.
- Citizens are 33% cheaper.
- Conquered cities are assimilated 200% faster.
- Military research at the Library 33% cheaper.
- Tanks initially cost a lot to research, but over time become cheaper than that of the enemy.
- Unique naval units and artillery have a science-based LOS, which increases with each level of science (yellow) technologies researched.
- Bombers and fighters take less time to build.
- Accuracy of heavy bombers from  onward is increased.
- Vehicles produced from the Armoury and Munitions Factory are produced faster and have ramp costs slashed for all materials except for oil.