United States
As British colonies, the original 13 states drove on the left-hand side. The switch to driving on the right started following independence, influenced by a number of factors, including wishes to cast off links to the colonial past.
The first keep-right law in the United States, passed in 1792, applied to the Philadelphia and Lancaster Turnpike, between Lancaster and Philadelphia. New York (in 1804) and New Jersey (in 1813) also enacted keep-right rules.
Early American motor vehicles were produced in RHD following the practice established by horse-drawn buggies. This changed in the early years of the 20th Century: Ford changed to LHD production in 1908, and Cadillac in 1916.
Many imported RHD cars are also found on the road in the United States, especially classic cars or other collectors' items.
Today, U.S. motor vehicles are always LHD (except some postal service vehicles, garbage trucks, many parking enforcement vehicles and uncommon specialty vehicles), and motorists always drive on the right and overtake on the left.
American rules of the road sometimes permit overtaking on the right side (multi-lane highways, one-way streets, or when overtaking other vehicles preparing to turn left). The laws vary from state to state.
The only U.S. territory where driving is on the left is the U.S. Virgin Islands.
The above was copied from Wikipedia.
There are virtually no restrictions on importing cars which are 25 years old or older. Mikeys_toy is 100% correct in the safety standards of newer cars being imported be it LHD or RHD and less than 25 years old. :n: