This is actually a regional bit of language, specifically the region of the US. The term ‘state’ originally meant (and in some places, still means) an independent and sovereign entity/government. Under the terms of colonial America, each state was truly independent, so the term makes complete sense. Even the original attempt at uniting the colonies (under the Articles of Confederation) maintained that independence.
But that failed and was promptly replaced by the US Constitution, which made the states much more like provinces. They became a piece of the whole, with significant influence from the larger entity. But we kept the term “state” when referring to them.
This is actually a regional bit of language, specifically the region of the US. The term ‘state’ originally meant (and in some places, still means) an independent and sovereign entity/government. Under the terms of colonial America, each state was truly independent, so the term makes complete sense. Even the original attempt at uniting the colonies (under the Articles of Confederation) maintained that independence.
But that failed and was promptly replaced by the US Constitution, which made the states much more like provinces. They became a piece of the whole, with significant influence from the larger entity. But we kept the term “state” when referring to them.