(1) "Adoption assistance state" means the state that is signatory to an adoption assistance or adoption subsidy agreement in a particular case.
(2) "Residence state" means the state in which the child is a resident by virtue of the residence of his adoptive parents.
(3) "State" means a state of the United States, the District of Columbia, the Commonwealth of Puerto Rico, the Virgin Islands, Guam, the Commonwealth of the Northern Mariana Islands, or a territory or possession of or administered by the United States.