米FAAは一部空域でADS-B OUTを義務付けているが、ADS-B INはそうではないそうな。

英語版WIKI、ADS-Bの項より、米国の実装状況

United States[edit]

To reduce congestion and cope with growing aircraft traffic, the Federal Aviation Administration has been developing the Next-Generation Air Transportation System (NextGen),^[13] including ADS-B. ADS-B equipment is built to meet one of two sets of industry standards, DO-260B and DO-282B.

Aircraft operating in the United States in the airspace classes listed below are required to carry equipment that produces an ADS-B Out broadcast. ADS-B Out broadcasts information about an aircraft through an onboard transmitter to a ground receiver, moving air traffic control from a radar-based system to a satellite-derived aircraft location system.^[13]

There is no such mandate for ADS-B In, which receives data and provides it to in-cockpit displays.^[52] The FAA airspace requirements intentionally exclude some airspace that is frequently used by general aviation.

Airspace Class Altitude

A All aircraft equipped

B All aircraft equipped

C All aircraft equipped

E Where above both 10,000 ft MSL and also above 2,500 ft AGL

Airspace Class	Altitude
A	All aircraft equipped
B	All aircraft equipped
C	All aircraft equipped
E	Where above both 10,000 ft MSL and also above 2,500 ft AGL

WIKI：Automatic Dependent Surveillance–Broadcast / Implementations by country / United States

wikiの引用元より。

The FAA has published a rule requiring ADS-B transmitters in many types of airspace (ADS-B Out) in 2020, but there is no mandate for ADS-B In, which receives data and provides it to in-cockpit displays.

www.aopa.org

trafficnews.jp

海保機がADS-Bを搭載していれば事故が防げたような論調が拡散されているが、JAL機にADS-B INの機能が無ければ今回の事故は防げない。ADS-B INの搭載は諸外国でも義務化されておらず、現時点で搭載機は圧倒的少数派。
監視装置の進化は必要だが、正確な発信が必要。https://t.co/KptJvJ1qVn
— motoいっぺい (@moto_ippei) 2024年1月15日