There are three major tech trees in War Thunder. Every tech tree in war thunder is different ranging from tanks that are big with big guns and lots of armor, light and fast tanks with fast reloading guns, or medium tanks that are good for dueling with other tanks. The Usa tech tree is a mix of all these three aspects. In a tech tree there are 2 main aspects to getting a vehicle. Silver lions (the virtual free currency of the game) and rp or research points (more research is needed to unlock higher ranked vehicles). The higher ranked vehicle you try to unlock the more silver lions and research points it will take to research and buy it. There is also a special currency called golden eagles (the pay for currency of the game) Moving on from that the Usa Tech Tree is a mix of Heavy tanks with lots of armor, medium tanks with fast reaction time to attacks due to stabilizers (makes the barrel stay still while moving so you don’t have to stop to shoot), and light tanks with punchy guns and fast reloads. For the Usa tech tree the top vehicles (last vehicles you unlock) are 2 light tanks with punchy guns and good reloads, 1 medium tank with good reactions time and mobility, and one anti-air vehicle (anti-air vehicles use either missiles or different types of guns to shoot anything from a helicopter to a plane out of the sky).