Is cryptocurrencies, or just bitcoin going to improve the US and Canada's economic welfare or condition all of a sudden? I highly doubt it.

Bitcoin is useful as an international and global currency with no central bank. I don't think that it's true to say that the United States and Canada's economy depended on cryptocurrencies, or that they are going to drastically improve due to it. Same goes for any other country, since bitcoin is completely stateless and there is no central entity controlling it the way fiat is controlled.

Bitcoin does benefit a range of people, regardless of their country or nationalities. For example, unbanked people can be helped greatly as bitcoin provides a means to save. Workers from remote regions can connect with global employment opportunities. etc. etc. It's not just restricted to countries.