**Neither a teacher nor a native speaker.**
"A European" is fully correct.
It depends on how you pronounce a word.
If a word begins with a spoken vowel, you'll need to use an.
This is an emergency.
My dad drives an extremely fast car.
An error has occurred.
It's an honor to help you.
I bought an MP3 player yesterday.
Pronounce all that words and pronounce the word European [Youropean ].
You should understand the difference now