For the record I'm an LIC resident and generally opposed to Amazon under the proposed plan

The entity that is charged the tax has nothing to do with who's actually paying the tax (in the real sense - the person who bears the burden of the tax). A sales tax that's added to a point-of-sales bill versus a sales tax that's invisible to the consumer and charged to the supplier has the exact same economic impact on both of them.

For example, FICA taxes are nominally paid 50% by the employer and 50% by the employee, but over 90% of the actual tax incidence falls on the employee. Even if we changed the law so that 100% of FICA taxes were paid for by the employer, employees' after-tax wages would be the same.