That would be a kick in the pants if a guy is floating along the top edge of a tax bracket and the stimulus money pushed him up into the the next bracket lol.
It could very easily happen.
It can’t though. The tax rate on income is on the chunk of income in that bracket. Anything you earn less than that (so before the stimulus) is taxed at the lowest brackets’ rates. Said in a different way, only additional income in a new income bracket is taxed at higher rates. You don’t take home less after taxes because your income goes up, ceteris paribus.