I wrote my doctorate thesis in international relations theory and taught Intro to IR courses where the difference between country, state, nation, and nation sta

I wrote my doctorate thesis in international relations theory and taught Intro to IR courses where the difference between country, state, nation, and nation state were covered in week one. You're right that there's a difference between country and nation state (and a difference between nation state and both nation and state, too) but in popular use - including politicians who should know better - the terms are interchangeable.