Even if that's true (there are ways, though) that doesn't somehow negate the idea that it would be better for the normal person on the street to be able to use a currency that -- while volatile -- retains its value better than the peso.
The idea isn't that the US Government will step in there and say "Here's some bitcoins use these instead" but rather that the people will decide to end up using them on their own, irrespective of policy.
Argentinians love dollars because compared to the peso they're a "safe" store of value that's not under the control of their government, and because so many people will accept them. Dollars are the de-facto secondary currency not because of policy but because of people. There's nothing that would prevent the people from deciding to use bitcoin or dogecoin or litecoin or argecoin if they so decided in the future.