I’m sure black folks would have fared much better under the British in the late 1700s, or the Nazis or the Imperial Japanese after we lost WWII. Or African warlords on any day. /s
Slavery in the British Empire was ended in 1833, or about 30 years before the USA.
Had there been no American Revolution, however, slavery in the larger British Empire might have taken a good deal longer to get rid of, as there would have been a lot more slaves and their master would have formed a much larger and more powerful interest group, as they did in the USA.