Countries / states and populations are very different and suit different strategies:
Population density, average age, the proportion of single / multi-generation households, huggy / distanced culture, public compliance & trust with government advice, maybe Vitamin D levels,
the state being able / willing to support enough of the population financially to stay home so they don't starve or become homeless ......
For a country like Uganda, median age 17, it makes little sense to lockdown
For a US state with v low population density,
people probably would catch it rarely enough and slowly enough that it's not a problem
For a city like New York or London,
not locking down would probably have meant carnage
In the UK, the Chief Medical Officer looked at Italy in early March,
... and warned the government of a "reasonable worst case" of ½ million dead,
with 80% of the population getting it with a death rate of up to 1%
Of course no responsible government should ignore their CMO saying that
and of course the CMO had to warn them