Even if it was a 'spy balloon' the fact that it took them a week to do anything (in which case it would've got a shit load of data it wanted plus a lot more), plus the fact that there were apparently several others that flew across the entire us in the past several years without them even recognizing it, doesn't bode well for them. It would also give china a glimpse as to their preparedness (or lack thereof) in terms of a problem