Why should they have to pay a global tax? What service did a global government provide them? At least you can say that the state and national government enforced contracts and provides military and police protection, as well as education, but under what logical basis should they pay a global tax? Confiscation?
I reckon that, with globalisation, the nation state is becoming obsolete as a concept
Only, I would argue, when things are going smoothly. When things are sh**t, then it can be something that people can cling to for hope.