Correct. "The majority of precursor chemicals for illicitly manufactured fentanyl come from China and are synthesized into fentanyl in Mexico. Fentanyl is then smuggled across the border into the United States" [1].
That said, "China remains the primary source of fentanyl and fentanyl-related substances trafficked through international mail and express consignment operations environment, as well as the main source for all fentanyl-related substances trafficked into the United States" [2].
> which makes it to the US through the wide open southern border
No. "Most of the illicit fentanyl coming across the U.S.-Mexico border is smuggled through official ports of entry" [3].
[1] https://home.treasury.gov/news/press-releases/jy1953
[2] https://www.dea.gov/sites/default/files/2020-03/DEA_GOV_DIR-...
[3] https://www.npr.org/2023/08/07/1192557904/part-1-investigati...