The key problem with a “consumption tax” is that it’s what tax experts call a “regressive” tax -- one that falls more heavily, as a percentage of income, on lower-income income persons. This is obvious when one considers that people with lower income tend to spend most or all of it on non-discretionary items like food, clothing, and shelter, so unless you exclude those categories from the tax, the poorer members of a society will be contributing a higher percentage of their income to the government than the wealthy. The value-added tax (VAT) in most countries in Europe is a current example of a consumption tax, though income disparities in most of Europe are less dramatic than in the Americas. So there’s a cart-before-the-horse issue with financing a borderless society with a consumption tax.
