I think it was in the late 70s in Las Palmas that I met an American who pronounced can't in the British way [kɑ:nt]. I found that quite peculiar. He told me he came from the vicinity of New York, I don't remember the town or city. Yet he pronounced words like last, past and half like Americans pronounce them. He was definitely a native speaker of American English and the only explanation he could offer me was that in the region where he had grown up people pronounced can't that way.
I wonder if anyone could tell me what that region is and how common this pronunciation is in the USA. As fas as I know, which may not be far enough, it isn't common at all.
The American way to pronounce the above words was very common in southern England when the first Britons emigrated to America in the early 17th century and that pronunciation persists in some parts of England.

I remember discussing this with two elderly ladies on a train in England in the 60s. One of them said she had said the Daily Telegraph [teləgrɑ:f] all her life while the other one said she had said [teləgræ:f] all her life. Both thought they were right - and I agreed! Emotion: smile
I have no idea, but I decided to answer because no one else seems to have noticed this thread. I think it's kind of rare though. If there's someone in the US who says "cahnt", it must be because they speak a micro-variety of English, very regional. But that's just a guess, I told you I don't have a clue, LOL. Emotion: smile
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I am a native New Yorker and I know of three ways American's pronounce can't. Cahn't is more likely to be used by someone speaking mid-atlantic english.
Caent is more likely to be used by a working class east coast american. Can't with the soft a is considered standard american speech.
In Frasier, the title character and his brother both use something more similar to the English prounciation for can't. For those who are not familiar with the show, the two characters are from New York and were raised by a very "sophisticated" mother, hence they speak with what is generally considered an "upper class" or "snooty" kind of accent. Most people from New York pronounce it "cæn't". If you go to Boston, it's the same sound but articulated even further back and sometimes nasalized, which I think sounds really annoying :\ . In my dialect (West US), it's cæn't, also, but I'd say ours is shorter and a bit more middle-of-the-road than in New York.