Article 'the' in Country Names
the + (adjective) + noun.
When the (adjective) is removed, a simple noun remains.
Country names without an article stand only for those countries.
Special Note of Interest for New Yorkers
Why do we say "The Bronx"?
The area was owned by a family named Bronck, so people would say they were going to visit the Broncks.
Spelling was changed to reflect the pronunciation.