National cryptocurrencies might be a good idea but advantage of bitcoin is that it is international, and wherever you live and pay, you don't need to exchange money.
Agreed. One of the core tenets of bitcoin, in my opinion, is that it's borderless --or international as you say-- and not centralized in any way. National cryptocurrencies won't work (IMO) because they violate the principals of decentralization. Open vs closed/government-based crypto is like comparing the internet to a closed off intranet.