Not making any excuses for NORAD, but a B2 bomber weighs 160,000 pounds, without fuel or payload. It has the radar cross-section of a bird, pretty much undetectable by radar. A balloon is also not detectable by radar.
It seemed like we only heard about the balloon from visible sightings in Montana.
The payload is detectable.
The satellite payload included big flat solar panels and the rest of the payload is the roughly the size and shape of a small bus. If this isn’t detectable then neither are small aircraft. They are!