From my experience this has almost certainly reversed, at least in reference to places I've lived in East and West Africa, as most men wear 3 piece suits or at least long trousers and shirts. Meanwhile in America, most people who work outside or in a non-arctic office will wear as little as they can get away with.
Believe me, it's still hot and arid and the sun is relentless during the day (very long days, but beautiful nights -- the stars are incredible). There is very little shade and most of that part of the continent is flat and in near-desert like conditions.
I lived directly off the okavango delta which certainly cooled things a bit and added a touch more humidity to the air, but this summer on the eastern seaboard of NA is one of the worst I've experienced.
My point? Culture.
Having said that, England is currently enjoying one of the best and longest heat waves we've had in years. I'm just thankful I work from home, most offices would frown on me showing up for work in just my pants.
I was once mocked mercilessly by a Brit when I told him I had forgotten my pants. I, of course, had meant my blue jeans . . . I was wearing shorts.