Even with the growth of crypto, I think it can not replace paper money. All governments in countries want to control their economies, if a society has only crypto money, how can they manage it? Moreover, in rural and remote areas where internet and computer are not available, paper money is still the most affordable.
Absolutely right. The national money of the states interact with the economies of these states, and the cryptocurrency cannot provide such interaction. Therefore, nothing threatens national money. The money of various countries has been going on for thousands of years and most likely will still go on for a very long time. When we, after three hundred years, enter into official contact with aliens, as Wang had predicted, something might change. However, before that the national money of the states will go to each state.
The need for national money and the transition to any calculations, including in the cryptocurrency, can only be in the case of the unification of states into one state of global scale or at least the union of their economies into one union on the principle of the European Union.