We do not know for sure the balloons were spy balloons, but if they were, then trump allowed spy balloons to fly over our military bases unmolested, and Biden shot the spy balloon down. If they were weather balloons, as China claims, then trump allowed spy balloons to fly over our military bases unmolested, and Biden shot a spy balloon down.
Now let's talk about the evidence. The balloons were bigger than any weather balloon, and changed courses to fly over military installations. I think that is evidence enough for Biden to shoot it down, and I question why trump did not even allow them to be investigated.