Earlier quoted context omitted.
Comparing disease outcomes at all is futile because they are incredibly sensitive to initial conditions. One sick person travelling in January made all the difference.
The serious outbreaks in the US and South Korea began at the same time. Arguably, South Korea’s circumstances were worse because there’s was driven by a secretive cult that hid their illness and misled contract tracers. Look at where both countries are today. An immediate, thorough response makes all the difference.
Your "at the same time" statement is off by a few days and off by a few days makes a huge difference in outbreak severity. That's why you need to keep in mind that small numbers of infected people and seemingly short time intervals change the result radically.