It's meaningless to discuss tax in isolation, you have to discuss it holistically. Saudi Arabia, for example, could have a tax rate of 0% and still provide for

It's meaningless to discuss tax in isolation, you have to discuss it holistically. Saudi Arabia, for example, could have a tax rate of 0% and still provide for all of their citizens because of the oil they are sitting on. USA has some similar advantages in resources and arable land which Europe lacks. So comparing like for like tax rates makes no sense. Or things like conscription, for example, allows the Government the power to spend arbitrarily, since they can set whatever wage they want for the conscripted citizens, in theory (thereby controlling their own cost). This may not show up in nominal numbers (since they're reporting a cost that they themselves set) - for example, see USSR in WWII. If reported in nominal income, the cost of the war would have been 3x as large as normally reported.