It's pretty straightforward to determine where someone works. You are physically in the USA when you do the work so you're on the hook for income tax. What the companies do is set up a bunch of companies in different locations. Then they manipulate their books so that the low tax companies show profit while the high tax locations don't.
But you're not getting paid. Your company is getting paid, and then you're using credit against your company's assets to pay your expenses. You, for all intents and purposes, are volunteering.
Maybe your company has to sell something to be legit? Okay, you sell the people who are paying your company toothpicks. They pay your company for the toothpicks, the labor is just incidental.
