It is true that the regulations in some states coincide with others, but it is not the general rule. In many cases the regulations are very similar with minor variations. It is certainly noticeable that some states regulate the use of restraint systems in much more detail than others.
In summary, you should be aware that in the 50 states and in all the associated territories, it is compulsory for babies and children to use an approved child restraint system. As previously explained, the criteria vary from state to state. In all of them the main factor is the age of the child and, depending on the state, their height and weight is also taken into consideration.
It also depends on the state whether it is compulsory or not for the baby or child to be seated facing the opposite way to the direction the car is travelling in (in 18 states it is compulsory).
In 48 states, as well as in the District of Columbia and Puerto Rico, it is compulsory to use booster seats for children who are too big for a child seat yet still too small for direct use of the car’s seatbelts.
In general terms it is fairly standard for babies younger than one year old (or who weigh less than 20 pounds) to be seated in the opposite direction to which the car is travelling (in some states up to two years old); that children up to four years old can travel in a front-facing seat; that children between five and seven or eight years old (and 57 inches tall) must use a booster seat; and that from that age upwards the use of seatbelts is compulsory rather than a specific type of child restraint system.
Many states do not allow children of less than 12 years old to travel in the front seats, even with a child restraint system (but it should be emphasized that there are state variations to all these circumstances, so check beforehand).
In all states and associated territories, non-compliance with the regulations incurs a fine (the amount depending on the state) and, depending on the circumstances, loss of points on the driving license (in those states where that type of license exists).
Lastly, the regulations for children travelling on buses should also be remembered. In this case there are very few states that oblige school buses to have seatbelts that can also be adjusted to the height of the child. It is only compulsory in California, Florida, Louisiana, New Jersey and New York. In Texas it is compulsory but only for school buses that have been sold after September 2010.