US record of 68,428 cases comes as Brazil's caseload topped 2 million and UN urged G20 to step up aid to poor countries.
Brazil's coronavirus caseload topped two million, doubling in less than a month as the US passed 3.5 million total infections.
UN aid chief says coronavirus support to poor countries has been so far "grossly inadequate", urging G20 to step up aid or "pay price later".
More than 13.7 million people around the world have been diagnosed with COVID-19, while more than 7.7 million have recovered and more than 588,000 have died, according to data from Johns Hopkins University.