If you think the novel Pudd’nhead Wilson was or was not racist you’re wrong because that damn book exists in a quantum state where it is both racist and not-racist at the same time, and is always the opposite state of what you want it to be.
Mark Twain as a writer somehow managed to cover every part of the white man’s relationship to Racism, from The Adventures of Tom Sawyer, which was a completely Racist book
And Puddn’head Wilson which tried so hard to not be Racist and to lay out clearly why Racism was wrong and ended up blindly stumbling into numerous racist tropes and views, all the while thinking he was doing good.
Twain’s first failing is that the book is written in the voice of an omniscient narrator that accepts the existence and categories of race.
In Huckelberry Finn everybody accepted that races were a thing that actually existed, and that each race had characteristics, but these could be ironically played up at the same as the narrator was far from all-knowing the narrative was not taken as being true.