is there a line, like the equator, between america and europe, where °F are automatically converted to °C?

Answer 1

There's also a similar line between USA and Canada. But the calculation is not automatic. To change from Fahrenheit to Celsius, just subtract 32, divide by nine, and multiply by five.

Answer 2

There's no line like the equator where °F are automatically converted to °C. Most of the world uses metric measurements, the U.S. is one of a very few number of countries that doesn't. The only real line would probably be the border of the country you're entering into.

Answer 3

I don't think so.

Celsius and fahrenheit are just 2 different ways to express the same quantity of temperature. Your question is like asking if you carry a brick over a certain line, will its pounds will convert to kilograms? No, they won't, there is no such line.