There is an alt-history story (whose title I wish I could recall) about an American time traveller who goes back to visit a young Alexander of Macedon and his t

There is an alt-history story (whose title I wish I could recall) about an American time traveller who goes back to visit a young Alexander of Macedon and his tutor Aristotle. To disguise the origins of his superior science he pretends to be from a far province of the Persian empire. Upon his return to his own time he is shocked to find a largely agrarian US still populated exclusively with its indigenous peoples - the European invasion has not happened. The conclusion is that Aristotle, and by extension the entire classical intellectual movement, was so intimidated and overwhelmed to discover this visitor's vastly greater scienctific knowledge that their own curiosity was extinguished, and hence Western civilisation was stillborn.