There are no countries that have only 3 letters in their name.
car
3-Ohio,Iowa and Utah
BSA is one.
Awl
47, all of them except Iowa, Ohio, and Utah. If you mean how many have exactly 5 letters in their names, then it is 3: Idaho, Maine, and Texas.
The only scottish port with 3 letters in AYR. This is a common question found is crossword puzzles.
Barbara
Elx is a city in Spain
A snake with a three letter name is a Boa
Laos (Lao People's Democratic Republic)
Tan and red that is it