The fifth fasted 110m hurdle sprint of all time is a Chinese sprinter. The fastest 60m split over 100 metres in history is a Chinese sprinter. Black people are largely absent from most strength and weightlifting sports. Where, you guessed it, Chinese athletes often dominate.
You need to stop thinking in stereotypes and actually look at the world.
But as for the fact that there are lots of big, strong, black people about, especially in America, can you think of anything that happened, say in the last few hundred years, that might explain why black people in particular were prized for their size and strength?
Can you think of any people who might have been motivated to specifically breed black people to be big and strong so that they could, oh, I don't know, work harder in a field or pick up heavy loads? Or just so that they might fetch more money at a market?
"Black people" is a huge, enormously diverse slice of humanity. There are small black people and big black people and all sizes in between. But black people who don't have a recent slavery lineage, surprisingly enough, aren't unusually big or strong.