Income tax makes up half of the revenue the federal govt collects. I have seen 4.4 trillion reported as revenue collected through all types of taxes. That means 2.2.trillion is from income tax and using your figure of 20% that's still 440 billion dollars. Thats a hefty number but more so if you consider that half of Americans pay $0 federal income tax.
As the federal government spends $6 trillion, not counting Federal Reserve shenanigans.
This is not sustainable.
