i find it amazing that "in one nation under god" there is not "one unified, nationwide sales tax, applicable on any and all sales, be they online or locally "offline". Federally collected to make collection easy and to make it easy [also for small/er] for retailers to do their accounting. And distributed to states based on some key. Percentage of population for example. Or whatever formula works best.
Where I live we have 20% [national/federally collected] VAT in general "on anything" purchased by end users/consumers. Basic foodstuffs, rent payments for private housing (!), public transportation tickets etc. are taxed at half-rate 10%. After a few years of "online shock" VAT is now also collected on online sales throughout / between EU countries. If I order from amazon US [if they ship to my country at all] will also be taxed at our applicable VAT rate.
Tax revenues are then distributed at federal, state and community levels according to some intricate formula, but mainly based on population numbers - but taking care of less densely settled rural states/areas as well.
Really interesting to observe how "un-united" the "United" States of America are in many regards.