The fact is "There is no federal limit on the amount of alcohol a person may import into the U.S. for personal use." In my state: "A California resident or any other person crossing the international border via common carrier may bring in a reasonable quantity of alcoholic beverages (up to five cases or 60 liters) provided the beverages are for personal or household use." Not sure what you think you saw at TTB, but read it over again. If you have concerns, don't do it. It's that simple.I would suggest reading up on the TTB.
https://www.abc.ca.gov/importing-alcoholic-beverages-for-personal-or-household-use/