And that's only if it's corporate profits; personal income from ANY source worldwide must be reported and is fully taxable, with at best a credit for the first ~$15,000 in taxes paid overseas (meaning if you paid taxes on the first $100,000 then you don't need to pay US taxes as well).
Uncle Sam demands a chunk of every dollar you personally earn, anywhere in the world, even if you never set foot in the US for the year.
Heck, if you spent more than 183 days over a 2 year period as a VISITOR to the US - not even a worker - then the IRS wants a cut of your income. Even if you're not a US citizen or legal resident!
The key is “personally earn”, these people don’t personally earn it.
They setup a shell corporation which earns the money and they only take out of the shell what they need.
There isn’t anyway to stop this practice, there is no way to hold an individual personally liable for the earnings of a foreign corporation.