The Chinese sent at least one (probably several) “meteorological baloons” over America:

This doesn’t look meteorological to me, by any stretch of the imagination; it has a large antenna array which probably serves the purpose of monitoring the frequencies that would get absorbed by the atmosphere before they reached orbit, and probably amplifies and relays the results to a spy satellite in the geosynchronous orbit above. Considering how long it took the Americans to shoot it down, we can consider the north-American airspace basically undefended from ICBMs.