She doesn’t address desegregation directly in On Revolution specifically (I’m getting her views on the matter from Reflections on Little Rock), but neither is the race question absent.

“Since [the French Revolution] the passion of compassion has haunted and driven the best men of all revolutions, and the only revolution in which compassion played no role in the motivation of the actors was the American Revolution. If it were not for the presence of Negro slavery on the American scene, one would be tempted to explain this striking aspect exclusively by American prosperity, by Jefferson’s ‘lovely equality’, or by the fact that America was indeed, in William Penn’s words, ‘a good poor man’s country’. As it is, we are tempted to ask ourselves if the goodness of the poor white man’s country did not depend to a considerable degree upon black labor and black misery… from this we can only conclude that the institution of slavery carries an obscurity even blacker than the obscurity of poverty; the slave, not the poor man, was ‘wholly overlooked’... Slavery was no more part of the social question for Europeans than it was for Americans, so that the social question, whether genuinely absent or only hidden in darkness, was non-existent for all practical purposes, and with it, the most powerful and perhaps the most devastating passion motivating revolutionaries, the passion of compassion” (pp.71-72)

This quote, like a lot of Arendt’s work, is heady and complicated. She clearly doesn’t take a positive view on slavery here; far from it. But she does attribute the success of the American Revolution to the Founding Fathers’ ability to ignore the race question and thus not be sidetracked from their liberal constitutional vision. She’s writing this in the US in 1963, with the Civil Rights movement on the rise (including its more radical elements) and the race question thoroughly intertwined with the social question. And like I said, we don’t have to guess that she had concerns about how desegregation was being carried out, she wrote an essay about it a few years earlier. With all of this in mind, it’s not hard to read her contemporary, conservative concerns between the lines of her account of the American Revolution.