The U.S. coronavirus death toll surpassed 10,000 at the start of a week that officials predicted would be America’s most difficult yet during the global pandemic, while the crisis in Britain deepened as the prime minister was moved to intensive care.

Confirmed infections in the U.S. were more than double that of any other nation, at nearly 357,000, with the death toll at 10,783, according to data Monday from Johns Hopkins University. In the 24 hours ending 8 p.m. on Monday, 1,164 people died from the coronavirus according...