And then look at Worldometer, you will see that there is no indication at all, that there will be a second wave worse than the first. Denmark lifted its lockdown a month ago, replacing it with sensible restrictions and social distancing. No hint of a 2nd wave.
Do you have any country in mind, where you think a 2nd wave could be worse than the first?
On the question of population density, are you suggesting that countries with high population density are more likely to experience a 2nd wave, or countries with low density?
It's plausible that countries or regions with high population density, may actually be less likely to have a 2nd wave.
Of course I agree with friendly international cooperation.
The combination of innate immunity and acquired collective immunity (or herd immunity) appears to be being born out.
Extended lockdowns come with their own risks to life.