If you read the linked article, you will find that the United States has laws that waive sovereign immunity for torts committed by people acting on behalf of the federal government. Which is what I assume would be alleged here.
That doesn't mean that they would win such a lawsuit, however.
They can waive torts, yes. Doing so is a very specific process.
Cops regularly get qualified immunity for absolutely egregious conduct. The military is not going to get successfully sued for shooting down a $12 balloon while acting in good faith on national security duties.
What do you think the "very specific process" involved for the federal government waiving immunity to tort claims? I assume that is what you mean by "waive torts" which is a phrase that doesn't really make sense. Since it is "very specific", can you describe it?
You ask what the procedure is, and then link right to it. Legislation giving citizens the right to sue in certain scenarios. Without the government's OK, no suing the government.
The decision here would be "there's no clearly established law that the US can't shoot down a balloon with an F-22" on qualified immunity grounds.
That doesn't mean that they would win such a lawsuit, however.