You don't seem to understand how the progressive taxation works. In U.S. you pay 0 tax on first ~20k income, 15% on the next 35k, 22% on next 40k and so on (random numbers). The 22% is what you pay on anything above 55k in this example. But for the first 55k you pay only 20k * 0% + 35k * 15%=5250, e.g. 9.5%
Not sure how you missed the second sentence, or why you would use made up numbers in your response when I provided the brackets.
In the U.S., as a single filer, you pay 10% on your first $9,875, 12% from $9,876 to $40,125 and 22% from $40,126 to $85,525.
It does end up at 13% of $72K, assuming the $10K standard deduction. Since only the initial percentage was posted, no one would have any way of knowing if it was coming from the total calculation or anywhere else.
Federal + FICA for self-employed is barely 30% for that income and state is going to be well under 10%. Flat tax states will be 3-5% (or 0%) and even California is barely 5% effective rate.