Motor vehicle registration and the rules of the road are, under the rules of our federal system, committed to local administration. A citizen of New York has no right to bring his motor vehicle into New Jersey except when actually engaged in interstate commerce. Even when so engaged, however, the operation of the vehicle is subject to local law.

So, each state is the judge of what it will allow on its roads. New York can exclude vehicles with glass tinted greater than 7.5%. The California emissions standard is in a pocket universe cereated by the Clean Air Act, which allows more stringent standards for vehicles domesticated in a State. The recognition of other states’ license tags is a matter of comity only except when the vehicles are used in Interstate Commerce, and in the case of commercial vehicles, the law is based on a web of interstate treaties that provide for allocation and sharing of revenues.

Windhshield tinting kills cops. States are allowed to regulated window tinting. Tough bazookies is that costs you money or hurts your business.

When you are resident one place, driving thru some other geography, you are bound by the laws of that state you are visiting. These laws may be different from where you live.
* proof of registration with you
* proof of insurance with you
* fault or no-fault state
* need to have a front license plate
* tinted windows
* tires designed for winter driving, outside winter months

Some laws may only apply to residents of that geography, not to temporary visitors, tourists

When you move into a state, such as to attend college there, you are required to get license for self and for car in that state after some # days. This varies by state.

Why would you want every vehicle and every driver in every state and province to conform to every law, and how much are you prepared to pay to make it possible? Or are you prepared to give up many freedoms that would come with making any and all vehicle requirements a stricktly federal jurisdiction? Drivers are expected to obey the traffic laws of course, but, under your scenario, most American visitors to Canada would have their vehicles seized for not having Daytime Running Lights. When the laws regarding vehicle equipment differ from one jurisdiction to another, they cannot apply all laws to visitors, it would end tourism and most jobs that involve travel to more than one location.