I am no airpospace defense specialist, nor are you. I leave the "how" to them, but we clearly have capabilities well beyond this. I will not pretend to know stuff like Ty, but if you want to fie on the hill of "we can't hit a giant balloon in the upper atmosphere", then good luck with that.
Further, if we couldn't do anything about it, then why was it only after the thing is in the middle of our airspace and news gets out that Blinken finally cancels his visit to China? They would have been demanding this to stop days ago, and the visit would not have been going forward long before now when China didn't comply.
No, they didn't know...the inept Biden admin and its diversity focused military appears to have caught with its pants all of the way down.