That is excellent mitigation, and would keep the virus under control here—if it is done early enough...
Tick, tick, tick....
“Tick, tick, tick....”
If you’re waiting for the US CDC, I suggest you wind that clock and not hold your breath.
I don't think that sort of national request on K-12 closure will ever be done in the US. It's just antithetical to our national culture and how we view the federal government's role in local affairs. But there will always be people who want the government to do something, anything to correct the problem, no matter what needs tp be done.
Such a request in Japan is better considered as there is a high degree of community conformity, but Abe's request was just that - and in fact some cities are not going along with the request. Time will tell if they made the right decision.
I talked with someone from Osaka today and she asked if she went to Japan over the summer, would the US let her back in in late August. I said I thought it would depend on the COVID-19 status in Japan. It was sad, as she seemed scared, but she talked with some friends her age and regained her composure.