If the U.S. has only suffered between 25% to 60% (613k) of the deaths that would have come about if no preventive measures were taken with COVID-19 (2.3m)
For the UK, they have suffered 22 to 37% (130k) of the deaths (580k)
0.1% of the U.S. has died from COVID-19, compared to the 0.5 to 0.8% that died from the Spanish Flu
0.2% of the U.K. has died from COVID-19, compared to the 0.6% that died from the Spanish Flu.
If there were no preventive measures taken place for either, the U.S. would have lost 0.7%, and the U.K would have lost 0.9%
So in the U.S., COVID would have been equivalent to the Spanish Flu and in the U.K. It would have been noticeably worse.

Sources:
https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(21)00029-X/
https://www.cia.gov/the-world-factbook/countries/united-states/#people-and-society
https://www.cia.gov/the-world-factbook/countries/united-kingdom/#people-and-society
https://www.ons.gov.uk/peoplepopulationandcommunity/populationandmigration/populationestimates/adhocs/004356ukpopulationestimates1851to2014
https://www.usdeadlyevents.com/1918-1920-influenza-and-pneumonia-pandemic-nationwide-820000-850000/
http://news.bbc.co.uk/2/hi/health/4350050.stm