An interstate highway system
Individual state highway departments. The Federal government provides most of the funding for Interstate & US Highways though.
No currently there are no interstate roads between Chicago and Omaha that are closed. Chicago is 470 miles from Omaha Nebraska.
The two types of road are national highways and state highways. National highways go anywhere and are owned and maintained by the government of the country (such as the Interstate in the USA). State highways are roads contained within a single state. The state government is responsible for maintenance of these roads.
Alaska is the only state without any formal Interstate roads.
No. You are permitted to drive a moped or scooter on most public roads, however not on interstate highways.
Public services
North and south
north to south
390 miles if you take the interstate, 360 if you take the back roads. Take the interstate.
They are usually referred to as MAIN roads. However, the main roads from Abu Dhabi to Dubai are very much like the interstate roads of the USA. Still many people like to say "main road", others may refer to it as the highway.
The American government began a system of paved highways in the 1930s. The Interstate Highway System was started in the 1950s and finally completed in the 1990s. These were huge improvements.