[BrianR]

My Japanese wife had no trouble with either sound. But she trained in English from an early age and could speak either language perfectly. For her, the problem came from reading... Japanese is totally different from English when it comes to writing and reading. It took her a while to switch gears and every once in a while she would slip in the Japanese character for something inadvertently.

My Mexican wife is nearly perfect in both Spanish and English but since the written characters are the same (almost) she has no trouble. But I know when she's been speaking Spanish for a prolonged period when she phrases English terms and they sound "off". Because she's thinking in Spanish and then translating to English and Spanish grammar is different. She took courses to drop her accents (both of them, Spanish and hick) when she went into broadcasting.