For U.S. English, the pronunciation for "can't" is [kænt] and for "can" is [kǝn]. (I'm using the international phonetic alphabet to write the pronunciation.) It's very important for ESL students to learn how to say the [æ] in "can't." Otherwise, Americans hear the word as "can." That's the real problem for my students (and not that other word you mentioned; LOL).