Most of the “money American tech brings in” comes from the magnificent seven. US software engineering salaries are high even outside of those. In fact, it's high even in companies that are merely burning investor's money.
there are plenty of american cos that bring in tons of money that are outside the mag7.
vc funded companies pay high so they can grow and eventually bring in lots of money, and america has the deepest vc pockets so it reaps the rewards of the biggest exits