With most country names, don't use an article, and never us a/an.
Country names are like people's names.
You can't say "I'm visiting the George." Therefore, you also can't say "I'm visiting the Spain."
Use the with countries that are a collection of something.
For example: States, republics, federations, emirates)
When writing about a group of people from a specific culture, use the + plural form of the noun.
To check your writing for articles with country and culture names, use the following steps:
Draw a box around country and culture names.
Add the if the country name is a collection. If not, don't use an article.
For cultures, add the and make the noun plural (noun + s or irregular form)
Common country names with the:
Common irregular plural forms of culture names: