It is reasonable to interpret your instructions as allowing countries that use "y" as a vowel in addition to "only [containing] one of the five vowels." So I was surprised to find Myanmar and Cyprus and Egypt not being accepted.
Are you talking about "y" as a letter (grapheme) or as a sound (phoneme) it represents?
My intuition as non-native speaker says that letter "y" represents in English ortography consonant ("yes") or vowel ("heavy"). In my native language Finnish it is always vowel /y/ (same as /u/, but front).
"Yemen" is written in Finnish "Jemen", with consonant (/j/ resembles /i/, but only /i/ as a vowel can be nucleus of syllable). Then there are vowel examples like "Egypti", "Syyria" and "Kypros".
My intuition as non-native speaker says that letter "y" represents in English ortography consonant ("yes") or vowel ("heavy"). In my native language Finnish it is always vowel /y/ (same as /u/, but front).
"Yemen" is written in Finnish "Jemen", with consonant (/j/ resembles /i/, but only /i/ as a vowel can be nucleus of syllable). Then there are vowel examples like "Egypti", "Syyria" and "Kypros".