Per Worldometers the US had 522,938 Covid deaths as of last Friday. At a .26% infection fatality rate that would mean about 201,130,000 or 60.53% of the people in the US have already been infected.
It would take another 64,700,846 people to get infected or vaccinated to get to 80% of the population.
On Friday, Worldometers reported 2,274 new covid deaths, which would require some 874,615 new infections at the .26% infection fatality rate to reach that number.
At that rate we would reach the 80% infection rate in the US in 74 days.
But if vaccines also provide immunity we could be there quite a bit quicker. Per Bloomberg's vaccine tracker:
https://www.bloomberg.com/graphics/covid-vaccine-tracker-global-distribution/
In the U.S., the latest vaccination rate is 1,735,053 doses per day, on average.