In his inaugural address, President Joe Biden targeted a threat to national security that already festers here at home: a “rise of political extremism, white supremacy,” and “domestic terrorism that we must confront” and “defeat.” Seven days later, the Department of Homeland Security issued a national terrorism alert based on “a heightened threat environment across the United States” due in part to the transition of a new president. On Wednesday, House Republicans met to discuss the future of freshman congresswoman Marjorie Taylor Greene of Georgia who, according to news accounts, “liked” a Ja…