"The cot–caught merger or LOT–THOUGHT merger, formally known in linguistics as the low back merger, is a sound change present in some dialects of English where speakers do not distinguish the vowel phonemes in "cot" and "caught". ...An additional vowel merger, the father–bother merger, which spread through North America in the eighteenth and nineteenth centuries, has resulted today in a three-way merger in which most Canadian and many American accents have no vowel difference in words like "palm" /ɑ/, "lot" /ɒ/, and "thought" /ɔ/."
Apparently there's a subset of American-English speakers that would pronounce "caught" as "kaat". I've always heard it like a longer/smoother "cot" though.
I'd say a good first guess is the "a" in "about" instead.
Yes, in my dialect of American English (raised in Southern California by parents from the midwest), "cot" and "caught" are pronounced almost identically.
I was also raised in Southern California, and both my sisters and I—all born in the 1950s—have had complete cot/caught merger since childhood. The local friends our age whom I surveyed informally about the distinction in 1975 or so, after I learned about it in a linguistics class in college, also had the merger.
Our parents, who were born in the 1920s, both made the cot/caught distinction. Our mother was from the midwest, but our father grew up in the same Southern California city as we did. This suggested to me that, with respect to at least this one phonemic distinction, our language acquisition was influenced more by our peers than by our parents.
I should note that my sisters and I were initially flabbergasted that anyone pronounced those words differently and had trouble hearing the difference, while our parents were upset to learn that we pronounced them the same.
That's also how it rhymes in northern Illinois (Chicago/Rockford/Quad Cities). I've never pronounced "cot" and "caught" alike. Using different pronunciations is a pretty good indicator that someone came from the Chicago area.
Thanks for the suggestion. It was difficult for me to think of an example without resorting to IPA, since my own American accent is fully cot/caught + father/bother merged.
Note that the sounds in these various languages are not exactly the same, but the "au" in "caught" is the closest sound in the native phonological inventory of a General American speaker (given said speaker pronounces "caught" and "cot" differently).
It's worth noting that "given said speaker pronounces "caught" and "cot" differently" is a bit misleading qualifier - there are many who have some difference between "caught" and "cot" (with "caught" being similar to "cot" but longer/smoother, with a clear differentiation), but it's clearly not the sound you intended that would match Italian "casa" and IPA 'a'; so pronouncing "caught" and "cot" differently apparently does not necessarily imply pronouncing "caught" the same way you do.
Also, if I listen to the audio examples at https://en.m.wikipedia.org/wiki/Cot%E2%80%93caught_merger then it's exactly the other way around, that the "merged" pronunciation seems like an appropriate representation of "a" in words like Italian "casa", with "non-merged" "cought" sounding very different from that?