Robert Casey writes:

Why do people outside the USA call countries "states"?

Because "state" means "country". It meant that to the US founders,
too: in 18th century English, they named us "The United Nations of
America", and envisioned each state as sovereign except in matters of
war and commerce.

Subsequent developments robbed states of their autonomy, and reduced
them to provinces. Pity.

Regards,
Len.