Why can speakers of some languages pronounce some foreign phonemes and not others? The usual explanation is that they don't grow up hearing and using certain sounds. I do not always hear the difference between Arabic gutterals and have difficulty hitting on the correct h for Muhammad. Most Arabs are unable to say p, and are unable to hear the difference between p and b.
But why are Jewish Israelis able to say w, which does not exist in Hebrew, while it gives Germans such a hard time? And how come some Israelis drop their h's, when the letter does exist in Hebrew? It's true that the latter is more of a tendency than a disability. The same tendency is also present in northern Britain. French speakers have a still harder time with the h.
Obviously the ability to pronounce certain sounds must be connected with exposure of babies and small children to hearing and using them. I wonder whether passive exposure to the range of sounds present in other languages would augment their later ability to pronounce them?