China is helping the US deal with its massive fentanyl problem — sort of

• China said on Wednesday that it's willing to help the US crack down on fentanyl.
• The US says China is a main source of materials for fentanyl that later ends up in America.
• But experts are skeptical that the deal, scant on details, will result in change on US streets. 

President Joe Biden and Chinese leader Xi Jinping agreed on Wednesday to crack down on fentanyl production, a move the US has championed as a key step toward subduing its opiate epidemic.