Structural inability? Direct taxes (without apportionment) were specifically banned in the constitution. The census existed to determine representation in the legislature, certainly this would have been good enough for collecting taxes had they actually been interested in doing so. It sounds like you are equating sales taxes with excise taxes. If I didn't know better, I would think you just made that all up, but perhaps you could post a link.
Also, lower income tax payers were disenfranchised until Andrew Jackson was President. This is important to point out because tariffs and sales taxes have the end result of raising prices on end items. This means these taxes are regressive, hitting the poor much harder than they hit the rich. That works a lot better for a political career if the poor can't vote to throw you out for doing that sort of thing.
I have paid plenty of sales taxes, but never once a tariff. I suppose you could also argue that credit card fees are regressive and raise prices, but not many people would take you seriously. In the post 9/11 world, everything coming across the border has to be inspected, and a small duty to pay for this is in no way unreasonable, yet free traders would have us believe that our freedom is being stolen from us while government makes up the difference by forcing us to share our banking records and pay taxes up to 4 times a year, while spending us further and further into debt. I look at the big picture and nothing I hear from the free traders makes any sense, even as they move the goal posts further and further back.
Yes you have. It's simply built in as a higher price. Sure, you didn't get a reciept handed to you that said "tariff fee $2.98" on it but the effect is still the exact same thing, meaning you paid more to cover the taxes.