It's not an American thing. It's a Greek thing. For the most part, /æ/ isn't used in Greek. See non-Greek vowel sounds (http://www.webtopos.gr/eng/languages/greek/gre_ipa_3.htm). Wiki says that it's used in some dialects, but I'm not familiar with them. In my Medical English courses, we were taught the Greek vowel sounds, and they didn't mention /æ/.
Also, Peter Shor shared a link in comment that I agree with. Accents do vary slightly from place to place and person to person in the US. Here's an excerpt:
- All three are kept distinct. This occurs primarily in the Northeast, e.g. in the accents of Philadelphia, New York City, Boston,
and Providence, Rhode Island.[sample 2] In the Philadelphia accent
the three-way contrast is preserved, but merry tends to be merged with
Murray; likewise ferry can be a homophone of furry. (See furry–ferry
- All three are merged. This is found throughout the United States and Canada, and is almost universal in the West.
- "Mary" and "marry" are merged, while "merry" is distinct. This is also found widely, but in only about 15% of speakers in the United
- "Mary" and "merry" are merged, while "marry" is distinct. This is found in the South of the United States and as far north as Baltimore,
Maryland, and Wilmington, Delaware; it is also found among Anglophones
Again, person to person, things change. For example, a woman named Marry/Mary/Merry/Merri may pronounce her name differently than others in the region, as well.