We know from Mesechet Yoma that we worry about even a small chance of danger, and even that supersedes other mitzvot, so why regarding Brit Milah where there is a certainly a small danger, we don’t say to push off the mitzvah?

The Minchat Chinuch explains that when a mitzva essentially, by its very definition, includes a certain element of danger, the Torah is saying expressly that the general rule of Piku'ach Nefesh, simply doesn't apply there. For example, a murderer who is sentenced to death obviously cannot complain: "that sounds dangerous!". Or when the Torah obligates Israel to go to war to conquer the Land of Israel or protect the People of Israel, inherently that always includes danger, and God knows that and nevertheless He commanded it, and so too regarding circumcision.