When listening to Johnny Foreigner speak our own language, we use a few rough-and-ready rules to adjust for accent, and infer what he is saying. These rules may be applied in reverse to produce coarse impressions: swapping l and r for Japanese, adding a vowel after every word for Italian, pronouncing w as v and v as f for German.
When it comes to our friends in the Anglosphere, we become more cosmopolitan. The rules are applied subconsciously, and with greater precision. This allows a New Zealander, say, to distinguish between Scots, Geordie, Manc, Scouser, Yorkshire and Cockney regional variations. Thanks to the preponderance of US cinema and TV, most English-speaking people can, with some ease, detect regional phonetic differences between South Boston, Long Island and New Jersey accents, let alone SoCal and Midwest dialects. (The stereotype still runs, though, that the “insular” US population can’t tell apart an English, South African and Australian accent.)
Of course, there are bugs in our accent-translation program, which prevent successful reconstruction (and imitation, if that’s your thing). Australians, in particular, have trouble reproducing the rhotic consonants of North American English; a very bad imitator will over-compensate by pronouncing a hard r in the middle of banana. And I’ve noticed that most English speakers outside North America have difficulty inferring which vowel sound to use when they reconstruct – in their own dialect – certain words initially spoken by an American.
The phonemes used in the US to pronounce the vowel in palm or father and the short o in hot or bother are identical (/ɑ/ in the International Phonetic Alphabet), and only subtly diferent from awe or caught (/ɔ/). In Canada, and for some US Americans, all three sounds may be identical. But for Irish, New Zealand, Australian and Received Pronunciation, the three sounds are distinct. Therefore, when an American uses the phoneme ɑ/ɔ, non-Americans must judge which of three vowels he really means! And there’s some evidence that we systematically make the wrong choice. The long a sound (as in ah!), being the rarest, is usually sacrificed for one of the other two. So, outside the US, the surnames of actors Jake Gyllenhaal and Mark Wahlberg are commonly pronounced as Gyllen-hall and Wall-berg. An American called Massimo or Juan will regularly be addressed overseas as Mossimo or Won. And, before he achieved global fame, the current US president was sometimes mistaken for that infamous Irish nationalist, Barrick O’Bomber. Which probably explains this: