First of all, I am an American, and my native language is American English. My home language or first language, on the other hand, is a contour tonal language, with multiple tones, probably 4 or 5, with a logographic writing system. When I listen to the Japanese audio, I instantly pick up on the sing-songy intonation of speech and pronounce as close as possible.
From what I read on Wikipedia, native Vietnamese speakers, when pronouncing English, will really emphasize on the intonation, as if they were Vietnamese tones. I personally feel the same way. I hear tones... or at least regard the intonation of speech as having tones.
I know that Japanese is a language with a pitch-accent. But I am wondering if native Japanese speakers can pick up a distinctive accent among people whose first language contains contour tones, as opposed to people whose first language is non-tonal?