What death rate? The death rate per case? Or the number of deaths per capita?
I assume you realize the outbreak is not over in any of those 4 countries?
I assume you realize one of the most effective countries at dealing with the disease didn’t shut everything down (South Korea)
There are a lot of variables.
mask wearing
Lockdown
Timing of the lockdown
Adherence to the lockdown rules
Population density
Demographic factors
General health of the population
Hospital capacity
Nurses per capita
Doctors per capita
Temperature
Cuomo says "much of this comes down to what you do to protect yourself."
www.forbes.com
Here is an article from New York talking about how the new cases in the heat of the upswing were from people who stayed at home. This information may be out of date right now.
There has yet to be a statistical study showing that a general lockdown is an effective strategy to deal with coronavirus. At least not one that I’ve seen.
In the United States the worst outbreaks have been New York and New Jersey who had some of the strictest lockdown guidlines. While there are breakouts in states that relaxed guidelines right now, they’ve yet to approach the levels seen in New York City at peak. I’ve not read any studies the past few weeks so I won’t cite sources about the studies showing there is no difference: those studies are likely outdated by now. The data could very well show that lockdowns in the forms they happened worked.
Anecdotally, I think some elements of the lockdown worked quite well and other parts of it may have even hurt and caused the spread to happen faster. For instance, when absolutely everything was closed more people were likely to break the lockdown and get together inside someone’s home which may increase the spread. When outdoor social gatherings were allowed people were more likely to adhere to the guidelines.
It May be better to have a medium intensity policy that people actually follow than the strictest policy that 70% of the population ignores or can’t adhere to.