Are chocolate brands taking countries temperatures into account?
It's simple: people in hot countries eat dark chocolate.  In Southern Italy, chocolate is dark as coal and almost as hard.  Mexican chocolate classically contains only cocoa, sugar, and spices.
Well-tempered dark chocolate, without dairy products, wax, or other additives with low melting points, melts at a higher temperature than your Kit-Kat does.
Per Gizmodo

Dark chocolate has a higher percentage of cocoa in proportion to milk fat, so it has a higher melting point. Dark chocolate melts in your mouth; milk chocolate is much more likely to melt in your hand.