Why is pizza pronounced Pitza?
tsa/, and when the word was borrowed into English, it kept that T sound. In the Italian alphabet, the /tts/ sound is written “zz”, so they spell it “pizza“, and when the word was borrowed into English, its spelling stayed the same too.
What’s the correct pronunciation of pizza?
It’s definitely “peetsa”, both in British and American English. There is no correct alternative pronunciation. If your accent imbues a subtle “d” sound, I wouldn’t worry too much about that and people should be understanding.