On a micro level, I live in the US and I don't know anyone who takes fentanyl. "Every corner" is likely journalistic hyperbole.
It started with oxys until the gov cracked down then everyone went to brown heroin until fent arrived.
Report of Fentanyl in coke circa 2018.
https://www.dea.gov/sites/default/files/2018-07/BUL-039-18.p...
https://www.npr.org/2021/07/05/1013203805/party-drugs-are-be...
It makes a lot of sense if you assume they're trying to kill everyone
paraphrasing> If you bought cocaine yesterday, please discard it. It may be the bad one.
One of the reports during the problem: https://www.theguardian.com/world/2022/feb/03/argentina-tain...
One report one year later: https://batimes.com.ar/news/argentina/one-year-without-answe...