In Seattle we have Amazon Fresh, which is home grocery delivery. I can generally get next-day delivery, so I can order groceries and anything else they have in the local warehouse (books, movies, whatever) and have it sitting on my doorstep by 6am the next day.

I can't imagine living my life without it. Seriously.

Opening physical Amazon stores would trigger a sales tax requirement in every state where it operates, regardless of whether or not Amazon is able to negotiate a federal override of the state right to collect taxes on e-commerce.

States do not have the right to tax Amazon, if Amazon does not have a physical presence in their state. That's not a "federal override" but rather is part of the constitution and is a protection against every state collecting taxes on every business across the country. No taxation without representation.

States do have a right to tax their individual citizens who purchase online. Unfortunately, most citizens do not comply with these state taxes (called "use taxes" because they aren't on a sale, the sale occurs out-of-state).