How does Ohio, a state, differ from Japan, which is also a state?

US GOV

The definition of state, for politico-territorial entities is an independent, sovereign, political power and/or community that occupy a territory. By that definition, Ohio is a state as much as japan in that they are both sovereign politico-territorial entities that occupy a territory.

However, the huge difference is that while Ohio is a state, it is not a country. It is a political entity which has its own government but which is a constitutive part of a larger federal union of states that make up the USA, a country. It is sovereign with respect to its reserved powers but it has delegated the most important aspects of its sovereignty to the federal government as per the Constitution. Japan on the other hand is a country whose form of government is a unitary constitutional monarchy.