Earlier quoted context omitted.
States are not required to register cars just because the federal government allows them to be imported or sold. They can add requirements consistent with their own laws, as California infamously does causing 49-state cars and parts. Whether categorically blocking kei car registrations is consistent with the laws of some of the states doing it is a question in some ongoing lawsuits, though.
Different US states' very unique interpretation of laws on certain things is something I have seen that needs explanation to foreign visitors and people who immigrate, from countries where there is one consistent legal code and regulation system of various products at the national level... Marijuana regulations and firearms (and limitations of different types of firearms) are two obvious examples. Other things like p…
Your examples are actually different state laws, not different “unique” interpretations of laws, which is a pretty big mistake for someone who talks about needing to explain the situation to others.