Does USA Gain Anything from Its Allies?

You mean besides prestige, power, the support of a significant part of the worlds military in its wars (and there are many), the ability to freely sell its products in the largest economies in the world, the ability cooperate with companies in those countries (like BAE Systems, you know that foreign company that is responsible for the technology that makes the F-35B what it is?) and so on?

Not sure what you want but the type of relationship the US has is different from say China but you should differentiate between OECD and NATO partners and others. WHY would you think that significant economic, political and military partnerships with the world’s richest and most powerful nations ISN’T giving the US something?