Final answer:
State and local police are primarily responsible for the enforcement of traffic laws. State police handle statewide traffic regulations, while local police have authority within their jurisdictions. Federal law enforcement has a more specialized and limited role in traffic law enforcement.
Step-by-step explanation:
The enforcement of all traffic laws and regulations, including both state and city laws, is primarily the responsibility of state police and local or county police. State police have the authority to regulate traffic on highways and enforce statewide laws. Local police, meanwhile, have jurisdiction within their specific towns or counties. Alongside these, there are also federal law enforcement officers who operate under specific government agencies, such as the FBI or DHS, but their role in traffic law enforcement is more specialized and limited.
In addition to the police forces, state governments also play a crucial role in regulating various aspects of public safety, including highway safety laws like those against cellphone use while driving. This power is part of the states' reserved rights to regulate the health, safety, and general welfare of their citizens. Thus, it is the state that issues drivers' licenses and enforces the traffic laws that come with the privilege of driving.
It is noteworthy that although there is no unified national police force in the United States, the layered enforcement by state, local, and federal officers ensures that traffic laws and regulations are upheld in accordance with the relevant jurisdictions and areas of authority.