The feds are already involved with interstate commerce authorized under Article I of the U.S. Constitution...So technically applying a flat interstate tax to keep goods and services moving via ecommerce isn't a far stretch IMO.
But here you are talking about a new fed tax. I don't believe that the feds can interfere with an individual State's right to control its own tax methods and rates. Nor, I suspect, would any fed sales tax be remitted back to the States.
In short, be careful what you wish for. You just might get it!