I don’t think this applies in the UK. American pronunciations aren’t really applicable to most British accents. “
Can” does have a flat A sound here and no one would say Hairy for
Harry.
I’ve lived in several places in the UK, with vastly different accents, and A-rən is the usual, with AIR-ən being a more affected pronunciation that I’ve heard probably once. They are distinct pronunciations. As a side note,
Erin is pronounced differently, too — it’s EH-rin. EH as in “bet”.