How hard is it going to be to shoot this object down?
It's going to be 50+ km high, on the edge of space, at a FL where only balloons can navigate. It is made out of latex, and may well be difficult to get a radar lock on - it seems that it was only found visually. And it's travelling slowly, which often makes it hard to target from a fast moving platform...
I suspect that the US authorities may not be shooting it down because they can't...