What are the regulatory, financial and legal concerns? Why are they a deal-breaker? If there were no concerns El Salvador wouldn’t need to ask any help, would it?
KYC and AML are some of the biggest regulatory and legal hurdles for bitcoin. On the financial side, tying your country to a coin whose value you can't control, and is known to fluctuate wildly, is obvious financial insanity.
Yes, cash is problematic for KYC and AML. That's why cash transactions and ownership are highly regulated in most of the world.
And gold's day-to-day value doesn't fluctuate nearly as much as bitcoin. Still, it does fluctuate too much, which is why the entire world has abandoned the idea of using it as a representation of the value of money.