A picture the united USCA in 1836. It broke into Guatemala, Honduras, Costa Rica, Nicaragua and El Salvador in 1841
Nicaragua is a nation in Central America, releasable by the United States of Central America. It is located in central USCA bordering Costa Rica to the South and Honduras to the north.
Following the breakup of the USCA, Nicaragua, along with Guatemala, Costa Rica, Honduras and El Salvador, became an independent countries. It is already independent in the 1861 setting.
All the five nations share the same primary culture, Central American, so the first steps of the strategy would actually be to try to conquer the other states of the former USCA.