US states are sovereign in the sense the term is understood in US constitutional law, but not in the sense used in international law and international politics.

US states are sovereign in the sense the term is understood in US constitutional law, but not in the sense used in international law and international politics. They would be autonomous subdivisions of a sovereign state in the latter sense. Sovereign states in the latter sense can delegate their powers to external entities (as they do in the EU), but they can also unilaterally choose to take that power back (as the UK did). The USSR was an interesting case when it comes to sovereignty. Legally its member republics were sovereign states, but that sovereignty meant little in practice. As a result of a weird compromise, Ukraine and Belarus were founding members of the UN, despite not being sovereign in the generally understood sense. There was a legal mechanism for secession, but in the end, the member republics ignored it and dissolved the union.