[1] This is in contrast to asymmetric federalism, where a distinction is made between constituent states.
[2] Australia also has territories, which are autonomous divisions with devolved powers, but are subordinate to the federal government and organized in varying ways.
This was affirmed in Coyle v. Smith[3] when the U.S. Supreme Court declared a provision of the Oklahoma Enabling Act which required the State capital be located in Guthrie, Oklahoma until at least 1913, as being unconstitutional.
However, the U.S. has a number of insular areas directly under the control of the U.S. federal government, with various degrees of autonomy.
The District of Columbia is not an insular area, but it is also directly controlled by the federal government with limited autonomy.