Only modern black nationalists believe that the Ancient Egyptians were black.
The Pyramids are thought to have been very difficult to build because they are obviously very difficult to build with the technology available at the time. Remember that they were ancient even to the Romans and the Greeks.
Thinking the Pyramids would be difficult to build has absolutely nothing to do with race or racism.
I personally chalk that sort of stuff up to living where the climate is set to easy mode.
Compare construction that predates building code in wealthy coastal California to poor rural Maine and you'll find the latter is routinely within spitting distance of compliant with modern code because that's just what you need if you want your project to resist nature for a "worth the effort of building it" amount of time.
It's only in the latter half of the 20th century that the field stops presupposing that Europeans are better than everybody else and they start trying to more objectively and holistically evaluate life in other societies and compare them. There's still a large contingent of popular anthropology that hasn't caught up to that memo yet, and the general field of pseudoarchaeology absolutely thrives on it.
There's a reason that people treat the methods of construction of the Pyramids as some unsolved mystery but not, say, the Colosseum. And it's not because we don't have the evidence for the Pyramids--we have the written records that discuss pyramid construction, we have the letters from the Pharoah complaining about his workforce!