[DoodleDawg]

Correct. It is not clear when or how the States ever ceded their sovereignty. It is clear they created a government and delegated powers to that government. It is clear that they agreed to not exercise certain powers of sovereignty while members of the Union. There cannot be 13 or 50 different foreign policies of a single government. Agreeing not to exercise some aspect of sovereignty does not cede sovereignty, see e.g., Panama or Hong Kong.

How do you define sovereignty?

[FLT-bird]

Sovereignty is deriving their power from no other source/exercising power in their own name.