If the US wanted to end the fentanyl and xylazine and nitazene epidemic, it would legalize the controlled manufacture, sale, and usage of the drugs being adulterated. This won't happen, because the 50-year-old War on Drugs is a load-bearing pillar of the US government.
Xylazine and fentanyl are already legally distributed in the US. I believe Xylazine is still unscheduled.
https://www.dechra-us.com/our-products/us/equine/horse/presc...
It's like if Canada wanted to end gun smuggling and school shootings, it would legalize the controlled manufacture, sale, and usage of the guns being banned. But they won't.
I live in Seattle, decriminalizing drugs didn't turn out that way here.