schijf 1 € 0 t/m € 19.922: 36,55%
schijf 2 € 19.923 t/m € 33.715: 40,15%
schijf 3 € 33.716 t/m € 66.421: 40,15%
schijf 4 € 66.422 or more: 52,00%
The maximum federal tax rate is 40%, with California's rate being something like 10%. Most people don't pay the high end. Rich people generally have tax accountants and attorneys that are able to navigate the overly complex US tax system to find every loop hole. The majority of taxes are paid for by the upper middle class.
That said, investing a dollar a day on behalf of your child and tracking the progress of the account with them over time would be a cool way to teach them about money. You could even give them the option of instead of receiving some portion of an allowance, invest that as additional money into the account. There's all sorts of possibilities.
You could even offer to let them withdraw the dividend each month as an allowance or let it reinvest.