Why do we pronounce "Guerrilla Warfare" like?

In Spanish, it would be somewhat like ge-ri-ya. Foreign words are rarely pronounced accurately when adopted in another language. This is because the 2nd language doesn't have the same phonemes (linguistic sounds) as the one that the word came from. There are at least 2 phonemes in the Spanish word "guerrilla" that don't exist in English, so we approximate the sounds.