Yes, about 2/3 of American English speakers don't distinguish among those sounds (or don't do it very clearly, in some cases). The ones who do make a distinction (though not all of them in the same way) are mostly found in the areas of early settlement along the East Coast and the Gulf Coast, plus adjoining inland areas.

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I'm not a native (or entirely fluent) speaker, so be sure to wait for confirmations/corrections, especially for tattoos.

I'll never forget the very first Irish instructional pamphlet I got (found in an antiques store in the late '70s)...it mentioned that one vowel sound was as in "nought" and the other was as in "not," and I'm going "but...but...they're the same sound!"

And yes...in my area, we make little or no distinction between "Mary," "Marry," and "Merry."

Redwolf

The popular Hugo "in 3 months" language learning series in the UK used to sell themselves on their "imitated pronunciation" system that made speaking "easier". The problem was, their symbol for schwa-like sounds was "er" as in "driver" -- taking a non-rhotic accent as a given. So when they brought out a Scottish Gaelic edition, the author said in the foreword that unlike other editions in the series, his book didn't use imitated pronunciation, as he didn't expect any of his readers to speak like that....

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A language belongs to its native speakers, and when you speak it, you are a guest in their homes.
If you are not a good guest, you have no right to complain about receiving poor hospitality.