India is a Commonwealth country, and I wouldn't be surprised if a lot of people still think in imperial (not US customary) units.
Also, here in the UK, for the purposes of identifying COVID-19 symptoms, a fever is being defined as 38.6 °C = 100.0 °F, so US recommendations are clearly having an influence in other countries.
There are different definitions of "fever" in medical websites. Some say anything above a person's normal average temperature is a fever, with it being considered a serious fever if the temperature is above 100.4°F.
Also, here in the UK, for the purposes of identifying COVID-19 symptoms, a fever is being defined as 38.6 °C = 100.0 °F, so US recommendations are clearly having an influence in other countries.