WASHINGTON—The U.S. faces a “heightened threat environment” from domestic extremists and people inspired by foreign terrorist groups with the approach of the holiday season, the Department of Homeland Security warned Wednesday. While DHS said it had no credible information on a specific threat, the agency warns in its latest national terrorism advisory bulletin that mass gatherings for the upcoming religious holidays could be potential targets, including from people and organizations seeking to exploit resentment over pandemic lockdowns and recent events such as the U.S. withdrawal from Afghanistan. “The Homeland continues to face a diverse and challenging threat environment,” it said. This is the fourth time this year the agency has issued a bulletin, highlighting the perceived danger from a volatile mix of domestic extremists, often motivated by racially or ethnically motivated hate, and homegrown extremists inspired by overseas groups. It reflects a shift from the focus on Al-Qaeda and other …