No country ends with the letter X.
Halifax
Some cities that start with x are Xi An and Xiamen both in China.
There is no country that ends in the letter X. There are, however, two countries that contain the letter X: Luxembourg and Mexico.
phoenix
A three letter word that ends in the letter x could be the word Hex. A hex is a witches curse or spell.
Mexico and Luxembourg are the only two countries that contain the letter x. As you can see, neither end in x, so there is no country that ends with the letter x.
Ibex?
phlox
appendix.
anthrax
t-rex