El Salvador has (and will have) negligible impact on both generation of and popularity of cryptocurrency, so I don't think that argument is very important given the far more pressing matters they have to deal with as a country, and ones they have control over.

The point about opening up a bank is interesting though. The amount of money WU is skimming off the top must be a non-negligible percentage of the country's GDP. There's gotta be a less pie-in-the-sky way to disrupt that without making El Salvador a money laundering haven, which will absolutely happen with this idea.