Hmm, I'd think that in a rhotic accent a word like "furlstrengths" or "fatherlands" would work better? In Japanese they sound like [ɸɯ̟ɾɯ̟ɾɯ̟sɯ̟tɯ̟ɾiĩsɯ̟] or [haɾɯ̟sɯ̟tɯ̟ɾiĩsɯ̟] and [hazaɾɯ̟randozɯ̟] respectively, rather than the native [fɚɹłstɹiŋθs] or [fɚɹłstɹiŋkθs] and [faðɚlændz]. Adjacent /rl/ pairs are a special challenge, there are multiple unvoiced fricatives that don't exist at all in Japanese, and consonant clusters totally violate Japanese phonotactics to the point where it's hard for Japanese people to even detect the presence of some of the consonants. By contrast Japanese [ɾaɾapaɾɯ̟za] is only slightly wrong, requiring a little bit more bilateral bypass on the voiced taps and a slight rounding of the ɯ̟ sound.

Some Japanese-American soldiers would be SOL tho.