Scaling up the population of one country and comparing to the US is not going to be a valid comparison. Korea is comparable in size and population to California

Scaling up the population of one country and comparing to the US is not going to be a valid comparison. Korea is comparable in size and population to California, but you would not judge the timing of the response of California against the response of, say, Kentucky. Singapore is a bit smaller in population than the SF Bay Area, but you wouldn't judge the timing of the response of Bay Area measures vs., say, Miami. There are 3 very good comparisons to make in Europe. Three different approaches and 3 different outcomes, in terms of peak cases, peak deaths, and timing of implementing various measures. Italy, Germany and Sweden would be better comparison/contrasts than Singapore vs. the USA. For the USA, compare on a regional basis versus the countries in the study. Exaggerating to make the point, It's valid to do this type of analysis, but comparing the attributes of a scaled up mouse to an elephant isn't going to be of much value.