Different states? Different counties! The US tax situation is set by state and county and sometimes city, so two Starbucks on opposite sides of the street may have different tax rates.

Now, of course, you can still solve for it by charging a price that in aggregate is enough to include sales tax everywhere, but the way sales tax is calculated currently that actually can make it more difficult (as you have to track the "real" price which you solved for).

Or, businesses could do like they do in Europe: set the same price after taxes in every state.

I’d love to see pricing include tax… and then I think about how difficult that’d be to implement online

And different cities. https://www.cdtfa.ca.gov/taxes-and-fees/rates.aspx