WASHINGTON—The chairmen of two congressional panels on oversight and trade on Thursday assailed Tesla’s expansion in China’s far-western Xinjiang region, where detention camps have drawn heavy criticism, and asked the electric car maker about its Chinese product sourcing. “Your misguided expansion into the Xinjiang Uyghur Autonomous Region sets a poor example and further empowers the CCP [Chinese Communist Party],” Democrats Bill Pascrell and Earl Blumenauer, who head two House of Representatives Ways and Means subcommittees, wrote in a joint letter to Tesla Chief Executive Elon Musk. Tesla made a New Year’s Eve announcement that it opened a showroom in Xinjiang, becoming the latest foreign business caught up in tensions related to the region. Xinjiang has become a significant point of conflict between Western governments and the Chinese regime in recent years. U.N. experts and rights groups estimate that more than a million people, mainly Uyghurs and members of other Muslim …