WASHINGTON — “Enough, enough,” President Joe Biden exclaimed over and over Thursday night, as he delivered an impassioned address to the nation imploring Congress to take action against gun violence after mass shootings he said had turned schools, supermarkets and other everyday places into “killing fields.” If legislators fail to act, he warned, voters should use their “outrage” to turn it into a central issue in November’s midterm elections. Speaking at the White House, Biden acknowledged the stiff political headwinds as he sought to drive up pressure on Congress to pass stricter gun limits after such efforts failed following past attacks. He repeated calls to restore a ban on the sale of assault-style weapons and high-capacity magazines — and said if Congress won’t embrace all of his proposals, it must at least find compromises like keeping firearms from those with mental health issues or raising the age to buy assault-style weapons from 18 to 21. “How much more carnage are we willing to accept,” Biden said after last week’s shootings by an 18-year-old gunman, who killed 19 students and two teachers at an elementary school in Uvalde, Texas, and another attack on Wednesday in Tulsa, Oklahoma, where a gunman shot and killed four people and himself at a medical office.