Even though none of us like Gary for what he has done for the crypto industry. But we should be realistic and accept the fact that turning bitcoin into a currency is a difficult task and the chances of it happening are almost zero.
For a country like the USA, it's difficult, but in general, it’s not impossible if a country is willing, and El Salvador is living proof of that. However, I don’t think we should take his statement too seriously. Investors in the US are probably fine with Bitcoin’s current status. As long as they can use it and the government acknowledges it, they likely don’t expect it to become a legal currency like the USD.