A trivial gripe, but an indication as to why so many drugs which are effective and available in Europe are not in the US.
Years ago, I picked up a bottle of Mucosolvan (Generic: Ambroxol, Fast Acting Cough Syrup For Family | Dosage & side Effects | Best Cough Syrup | Mucosolvan® ) somewhere in Europe to deal with a cough and took it home with me. Once it was finished, I discovered this very effective product was not available in the US and made it a poiint to resupply whenever we went to Europe (I have had bottles with lables in a wide variety of languages over the past decades).
It was patented in 1966 and the patent is expired. Given its age, it’s unlikely that safety studies done at the time would meet the FDA’s current requirements. It may not be enough of a profit center for any single drug company to bother with the clinical trials that would be needed to pass the FDA, and ultimately, the answer is likely nobody thinks they could make money off it. Which is a shame, because it’s really good stuff.