###I don't think such a merger is common in general
Even though /æ/ and /ɛ/ tend to have similar realizations, I haven't read of a general merger between the vowels of bend and band being common in any variety of English.
My understanding is that /æ/ generally has a longer duration than /ɛ/, and I think that this applies also to the raised allophone of /æ/ that appears before nasals, and that is often transcribed as [eə] or [ɛə].
As Peter Shor mentioned in a comment, some American English speakers merge /ɛn/ and /ɛm/ into /ɪn/ and /ɪm/, which would increase the difference between the pronunciations of band and bend.
###Vowels in unstressed syllables are more likely to merge because of vowel reduction
The word and is a special case because it is usually unstressed and very often reduced to [ən] or [n̩]. Some American English speakers are known to pronounce /ən/ (e.g. in words like student and moment) in a way that sounds similar to /ɛn/ (see my answer to the Linguistics SE question "When should I use /ə/ or /ɪ/ and why does it seem like they're not used correctly?" for more details). For me, the words and and am are rarely pronounced with a fully unreduced [eə] sound; they are often reduced to [ən~n̩] and [m], and they might have partially reduced pronunciations that could sound like they have [ɛ].