The National Guard is effectively the militia of each state. They report to each governor first, and if activated, report to the US military. A traditional guardsman has a civilian job, 9-5 M-F, then one weekend a month 'drills' as a part of the unit. You can get activated, at which point your civilian job has to let you go serve. Most common activations are for statewide disasters--tornados, floods, hurricanes--but most recently medical units were deployed for covid relief. National callups would be to help the us military in Iraq etc., but at all times the guard serves the state first.