I find no mention of a river named Mediterranean River" anywhere on the internet There are many rivers, running through many countries, around the Mediterranean Sea.
The Black River is in the United States, it runs through no other countries.
Canada
Russia
Venezuela
Romania.
SPAIN !
India and Bangladesh
The River Thames runs through one country; England.
The United States and Mexico.
The United States and Mexico.
The river Severn flows through England and wales
Russia (Siberia) China