 issue. NPR's John Rewich reports Vance has said that China is the biggest threat to the U.S. Republican presidential candidate Donald Trump named Vance as his running mate on Monday as the Republican National Convention got underway. And later on Fox News, Vance said Trump would negotiate to end the war in Ukraine so America could focus on China. He called it the real issue and the biggest threat to our country, which he said is distracted from it.