The members of Congress are selected by U.S. citizens and funded by international U.S based companies operating globally. This creates a delicate balance where the interests and goals of all major economies are balanced. The U.S citizens maintain full control of who they vote. At the same time the influencing working trough their mind, and trough their representatives ensures what they decide is for the benefit of the all.
A small fraction of relatively ignorant individuals can vote freely with selfish motives, but the system still works as a global government. Everyone in the world who controls market access or money can have a voice.