The American planes are very middling. They're excellent at diving, but several of them have real trouble climbing quickly, and even the good ones can't out-climb good climbers in other nations, except maybe the P-38. However, except for some of the early ones up to about the P-40, most can manage extraordinarily high altitudes and can outperform almost everything else at those altitudes, so sometimes your best option is to climb until you're at 10000m and wait for some poor sap to come to you.
A lot of them are also surprisingly good at turn-fighting despite how they've been portrayed, but you generally don't want to get into a turn-fight with a plane unless you're confident you can outperform it. Form my limited experience, most German planes except the Stukas are a yes, a handful of British planes can be out-turned, and some Russians. Japanese are almost universally impossible to out-turn, and a lot of them can't be outrun either, for those you either want to force them into a head-on or avoid until you have more energy or more friends.
The Americans have notable advantages in two areas, but these are usually pretty minor unless the game gets dragged out. They're extremely hardy compared to other planes, even the 'UFOs' of Russia are only slightly better. The Americans also tend to have higher ammo stocks, even on the few planes armed with cannons, allowing them to blow more of their bullets plinking away at enemies as well as letting them not have to drift back to home base quite as often. The latter means that they can often chase down enemy planes that are out of ammo and fleeing for home, though this often means games are decided by whether the enemy airfield's AAA does its job or not, which is a gamble at best for both parties involved.