The shootdowns did not involve using airplane guns/cannons. Those are less accurate, especially at the engagement range (the aircraft were at 40,000 ft., IIRC, and shooting at 60,000 ft. balloons), and would have likely damaged the payload.

The shoot-downs used AIM-9 Sidewinder missiles (per TFA). We also don’t know the ceiling altitude of the F-22 since it’s classified.

However, the F-22 can carry the AIM-120 Advanced Medium Range Air to Air Missile (AMRAAM) which has a disclosed engagement altitude of 70,000 feet - capable of engaging even higher altitude balloons than these. As I understand it, the Extended Range AMRAAM-ER is believed to have an engagement ceiling of 85,000 feet.

Meanwhile, the US also has the Terminal High Altitude Area Defense (THAAD) anti-ballistic missile system, an air defense system capable of engaging targets at very high altitude. While its capabilities are classified, its max engagement altitude is at least 490,000 ft. or 93 miles … though using it to attack a balloon is like swatting a fly with a sledgehammer. THAAD is mobile and could be deployed in response to a high altitude balloon threat (some of which can fly 120,000 ft.)