That is right, I haven’t read the book, and I’m probably never going to. I’ve read some of Diamonds other work, and I have heard this argument a lot (particularly about the animals) and like you said, there is a lot of self evident arguments against it. Not just the fact that there were domesticated animals in the Americas, but also like the buffalo existed (and was probably semi-domesticated like the reindeer in Sápmi) and could probably be domesticated just as easily as the Water Buffalo in Asia.
But I have a deeper problem with Diamond’s book, and the main reason I will probably never read this book, is the fact that I believe he is asking the wrong question. The question of European colonization should not be about capability, but of consequence.
Brutal armies have in the past from all over the world been able to siege, occupy, colonize and genocide vast areas with nothing superior but their brutality. The Mongol army for examlple might have had a superior breed of horses, but what they had above else was complete disregard of the human lives of their victims. Same with the Huns, or the Japanese imperial army, and yes, colonial Europe.
Guns Germs and Steel (the explanation, not the book) sound to me like a post hoc analysis, an overfit if you will, to fit history neatly between the lines, and tie it together with a nice bow. Asking the question, „but how could Europe do this?“ is an extremely colonialist thing to do, a euro-centric world view. If Jared Diamond wanted to do history, he wouldn’t ask this question. He would ask: „what were the consequences of actual people victims of these crimes?“ Yes this is ideology, but I would argue that Diamond is also full of an awful world view which doesn’t fit in historic analysis of this century.