I suppose I just don't believe that would happen. You can still practice social distancing/face masks/hand washing without shelter-in-place. I believe those three things alone would significantly slow down the spread to manageable levels. So I simply don't see a scenario where it "grows unchecked" to millions in the USA. It would hit millions eventually (like swine flu) but it would be manageable (not "unchecked"). Most of the US is geographically separated and not densely populated (except for cities like NYC), and we are only at 3M cases globally and that is with months of growth.

Lastly, even if it grew unchecked, I don't believe overwhelming the healthcare system would crash the economy. It might devastate the healthcare industry, but it wouldn't devastate all industries like prolonged, no-end-in-sight lockdowns are doing. I also don't believe it would "kill [significant amounts of] young people" because I believe the mortality rate is much lower than currently estimated.

Suicide is already killing more young people than covid-19 due to lockdown. 2 USAFA cadets committed suicide because of lockdown orders this month, yet 0 cadets have died from covid-19.