You wouldn’t pronounce “cat” like “caw-t”, would you? So why do Americans say the word pasta with a long a?
After a little digging, I learned that the Italian pronunciation uses a broad AWW sound, and Americans simply use this original pronunciation, resulting in “Paw-stuh”.
Across the pond (in Britain and the UK) they did not adopt this pronunciation of the word, and are left with “pah-stuh”.
Mystery solved. And your next linguini meal might start with linguistics trivia.