ST. CHARLES, Mo. (AP) — The startling news of President Donald Trump’s COVID-19 diagnosis serves as a reminder of the pervasive spread of the coronavirus in the United States. Health experts say it also shows how tenuous of a grip the nation has on the crisis. U.S. infections have been rising for several weeks, a worrying sign with colder weather approaching. The response to the crisis rests largely with governors, which has meant “a crazy quilt” of approaches, in the words of one health expert. The U.S. leads the world in numbers of confirmed infections and deaths. About 40,000 Americans a day learn they’ve tested positive.