I think you haven't considered that the effects of a weaker health infrastructure in underdeveloped countries are massively outweighed by the stark, exponential increase in hospitalisation rate and death rate with age. Developed countries may have more ICU beds but not 100x more. The death rate rises very very steeply with age for this virus.

Here's a comparison of deaths per million population in a selection of countries as of today (from worldometer). It correlates primarily with the median age of each country, even if they're developed.

Pakistan : 38

UK. 1274

Mozambique 4

Belgium. 1486

Nigeria 6

Usa. 867

Zimbabwe. 19

Italy. 985

Uganda. 4

Congo. 4

Spain. 989

Here's a study of seroprevalence in a region in Nigeria. It showed 25% seroprevalence in June so it has already spread widely in that country. Still, Nigeria currently has a population fatality rate of 6 per million. Median age in Nigeria is 17.9 years.

https://www.medrxiv.org/content/10.1101/2020.08.04.20168112v1