That's the problem. 20% are NOT mild...they require medical attention.
There are something like 964,000 total hospital beds in the USA.
If only 3,000,000 people get infected that's 600,000 hospitalizations. It would take far less than that to overwhelm our health care system. THAT'S why governments were trying to stop it. The US just didn't even try really.
And even less ICU beds, which is what the severe cases seem to require.
You keep noting the 20% number.
Is that the rate from... where? Japan, South Korea? Italy? China?
Like our “just in time” supply chain and logistics systems, our hospitals eschew an excess inventory of anything, including beds, ventilators, etc. Even if hospitals cancel all nonessential procedures (which would cost them a huge amount of money), there won’t be enough beds. There will be nowhere near enough ventilators. Best hope is to slow this down, or find a drug/treatment that averts crashing our healthcare system.