A record 1,080,211 cases were reported on Monday - the highest one-day tally of new cases anywhere in the world, according to Johns Hopkins University.
The Omicron variant accounts for the majority of cases in the US.
The top US pandemic adviser Anthony Fauci has said the country is facing "almost a vertical increase" in cases.
He said the peak may be weeks away.
While rates of death and hospital admissions in the US have been far lower in recent weeks than in previous infection spikes, the number of hospital admissions has been steadily rising.
