There is a false assumption here, that easy to understand makes it more palatable. A flat capitation would be even easier to understand, and even less palatable, because the ease of understanding is directly connected, in its case, to the ease of opponents organizing against it. A flat consumption tax faces a similar problem, which is why the efforts to push one to replace the income and payroll taxes for decades now under the label "Fair Tax" have been unsuccessful -- easy to understand isn't a political benefit when people who understand it often don't like what they understand.
But we know one thing as a fact: MOST OF IT was WRITTEN by Washington DC lobbyists specifically to embed in it all the loopholes that make it so that the elite in this country will pay hardly any taxes at all. Basically the fox guarding the hen house.
The obvious solution is to throw it ALL out and go with something simple that everyone understands. The reason this doesn't ever happen is because those same K-Street lobbyists make very large financial "contributions" to the same politicians in DC whose votes are required for a change.
Insofar as simply "choosing to spend elsewhere (outside USA)", somehow sales-tax is something people find difficult to avoid already right? We're just talking about increasing existing sales tax amount, and then eliminating all Federal tax.
Of course since a consumption tax hurts the poor disproportionately, the gov't would send a refund check to them, in large enough amounts to make up for it, where the poor are basically paying zero tax.
It also fairly discourages illegal immigration because illegals wouldn't get that kickback check from the Gov't, since they're 'visitors' not 'citizens'.