Ships fielded by the United States Navy (USN) sport great armor (albeit in an all-or-nothing design), main battery guns, and anti-aircraft (AA) capabilities, and are less hindered by stock configurations — many were built later and subsequently underwent fewer, less drastic upgrades (unlike Imperial Japanese Navy (IJN) vessels such as Kongo). Most stock American ships are adequate for their roles, and while fully-upgraded ships perform better, they require little to no change in play style. American ship-launched torpedoes are often comically bad, but the real strength of USN ships lies in their ability to get into firefights and slug it out, relying on their superior guns and survivability to see them through.
Arguably, the United States inherited its nascent naval traditions from the British, from whom they won their independence in 1776. Over the years, the USN encountered various hurdles and successes in its conflicts with the British, French, and Spanish navies. However, a mix of poor economic outlook, isolationist sentiments and post-World War I naval disarmament treaties reduced the effectiveness and preparedness of the USN for the Second World War; all of that changed after Japan's 7 December 1941 surprise attack on Pacific Fleet headquarters at Pearl Harbor, Hawaii. Regarded as an underhanded sneak attack outside the rules of civilized warfare, Pearl Harbor evaporated any reluctance of the American public to go to war.
With its battleship fleet crippled by the Pearl Harbor attack, the USN turned to submarines and its fledgling aircraft carrier fleet — the very weapons that the IJN had used in their attempt to neutralize the USN Pacific Fleet — and ironically put them to greater effect than the Japanese (who stuck to battleships and the "decisive battle" doctrines), achieving successes in the battles of the Coral Sea, Midway, the Philippine Sea, Leyte Gulf, and Okinawa. While slightly behind their IJN counterparts at the onset of the war, the USN gradually caught up both qualitatively and quantitatively; virtually every class of vessel was outfitted superior fire control equipment such as radar and ballistics computers. The industrial might of the United States produced large numbers of proven designs (the 175 ships of the Fletcher class built within the space of less than four years being a prime example) with little unnecessary variation in equipment, so that crew transferred between ships could quickly fill their roles without specialized retraining. The US Navy emerged from World War II as the most powerful navy in the world.
The play style of American destroyers is best summarized as "annoy and harrass"; their fast-firing guns in quick-turning turrets can continuously rain fire on opponents with impunity while under cover of smoke or vision blockers such as islands (or simply out of vision range). Tier X Gearing, the crown jewel of USN destroyers, can blanket her targets with more than 120 rounds per minute. Unfortunately, slow shell velocities and incredulously high shell arcs, while allowing captains to fire over islands, make it near-impossible to hit anything but the largest of targets beyond medium ranges. They also have reasonable anti-aircraft firepower, allowing them to play the role of escort ship when the need arises; fire discipline and astute Smoke Generator usage are required, since gun and anti-aircraft battery fire can broadcast a ship's position. USN torpedoes had variable speed settings; in World of Warships, only the high-speed setting is available (with the exception of Tier VII premium Sims). In-game, this means that lower tier American destroyers, instead of stealthily launching a spread out of visual range, are forced to weather fire from their targets' primary and secondary batteries well before they come within torpedo range. However, starting with Mahan at Tier VII, it is possible to launch a torpedo salvo from beyond detection range, albeit still at shorter ranges than their Japanese counterparts. To put things in perspective, Americans have to wait until their Tier IX's Fletcher before they get torpedoes with 10km range; the Japanese achieve this range with Tier VI destroyers Hatsuharu and Fubuki... and both of them reload faster.
American cruisers are all about the guns; their primary battery, secondary battery, and anti-aircraft armament are superlative. Forgoing torpedoes after Omaha at Tier V, they are instead able to lay down an incredible hail of gunfire in almost any direction, due to the fast-firing guns located along the sides of their lower-tier ships, or in their fast-turning turrets at higher tiers. Any enemies - especially destroyers — that come within firing range and do not take evasive action are quickly sent to the bottom of the ocean. Although the Japanese often have better range and firepower, the Americans have faster turret traverse, conventional layouts, and higher rates of fire; the high shell arc of some of their cruiser rifles — like their destroyer counterparts — is a double-edged sword, with a plunging trajectory hampered by their unimpressive shell velocities. Their anti-aircraft batteries easily dissuade aircraft from venturing too close or even approaching if they're not massed together for protection; yet even then, a well-timed Defensive AA Fire will quickly deplete the assets of enemy aircraft carriers. Des Moines is the very pinnacle of the all-gun cruiser, as she has a very powerful anti-aircraft suite and main batteries that have unrivaled rate of fire.
American battleships follow more orthodox and consistent designs: while their guns may not be as large and powerful as those of the IJN, the USN ships make up for it by having more guns that fire more often, giving them unmatched broadside firepower. In spite of inferior firing ranges and speeds, American battleships are capable of absorbing major damage in order to bring their guns to bear—their citadel armor is impenetrable to all but the largest caliber shells (at the cost of having a more lightly-armored bow and stern). Moving up the tech tree, their mobility progressively improves, and catches up with the Japanese with Tier VIII's North Carolina. The Tier X Montana is the pinnacle of the American battleship line: the evolution of the Iowa battleship design whose construction was cancelled some time after receiving Congressional approval for construction in order to focus more on aircraft carrier production.