My concern is that this "curb in spending" won't be a little but a whole lot. I can't imagine the size of sales tax that we would have to pay.
The only countries that don't have an income tax can fund their gov either through large per capita oil wealth that is largely state owned or through substantial tourism taxes. The US has neither option. I can't find any working examples of just relying on Sales tax. What makes you think that the downward pressure on spending won't send us into a prolonged depression?
No idea. I'm not an economist, but I do know that having around 50% of the populace on welfare and incentivized not to work ain't working either. Maybe if we quit expecting Uncle Sam to be our wet nurse, the sales tax wouldn't be that high. There are billions, if not trillions, spent on things you can't find anywhere in the Constitution that the federal government is responsible for.
This would be a kick in the head: Take all the things the federal government doles out money to. Divide it between those things that are Constitutionally authorized and those that aren't (UN Payments, Ukraine, etc.). Set up a consumption tax that will cover the Constitutionally authorized expenditures then ask for voluntary contributions for those that aren't, line by line. If it doesn't get funded voluntarily, it goes away.....
I know I'm just talking out my butt, but I'm retired at 61 after having saved up enough to retire. My number one expenditure every month is taxes, taxes and more taxes. I'm not eligible for SSN or Medicare yet, but I did pay a crap load into those over the years, so I don't consider them welfare. Those are sunk costs, my current taxes aren't going towards those.
I've mentioned before, I've been on two city councils. My claim to fame is we were able to adjust to live off just sales tax, no property tax, in both cities. (Yes, I know those are local not federal) But I bet if enough smart people (I think this is where my argument falls apart) were to get their heads together, they could figure it out.