Shooting down a balloon at 60000 + feet is a lot harder than a layman would think. This article may help in an understanding of what seems like an easy task is not.
Why Shooting Down China’s Spy Balloon Over The U.S. Is More Complicated Than It Seems
Also not mentioned in this article is the fact at 60000 plus feet the air pressure inside the balloon is not much different than outside. Putting a bullet hole in it would be like letting the air out of a giant warehouse by opening a tiny window.