Of course this was very early and US didn't have many confirmed cases. And to be fair singapore government also didn't recommend it yet at that time, possibly due to shortage of masks and health care workers were given priority.
At that time, the 'experts' in the West were telling everyone it was not necessary for people to wear masks, even though it became standard practice in China. They believe masks were not effective. Just wash your hands thoroughly. Singapore was no different.
It was only much later when the number of cases went up dramatically in the West that wearing of mask became standard practice. Even then Donald Trump was reluctant to wear his mask.
Another thing that shatters the superiority myth is the ranking of countries best prepared to deal with pandemic. Somehow they have got it upside down.