Proper Nouns with THE
We normally use "the" for country names that include "States","Kingdom", "Republic" etc:
States
the United States of America/the USA
Kingdom
the United Kingdom/the UK
Republic
the French Republic
We normally use "the" for names of canals, rivers, seas and oceans:
canals
the Suez Canal
rivers
the River Nile, the Nile
seas
the Mediterranean Sea, the