Only ADR I know of refers to Australian Design Rules.
Means that it complies with the australian law for street use......
Compliance with ADR may not help in the USA.
Here in Australia many bikes that were dirt only in the USA are road legal with an ADR tag.
Example: 1981 KDX 175 from Kawasaki. A two stroke dirt bike. The Ozzie version had light switches, horn, and tail/brake lights when ADR compliant. Not all were.
Example: The Honda XR 250/400 series was ADR compliant and used on the road here.