Japanese accent?

I'm American English speaker and I'm learning Japanese and Chinese (been doing Japanese longer). I was wondering about my accent. When I speak normally, I can pronounce the words correctly but even though I'm from America, I can tell that if Asian people heard me speak, they'd know I'd have an accent. I can do that soft nasal kinda childish Japanese girl accent (like Morning Musume). Also when I don't speak Japanese like that, I think I drag the vowel sounds out too long. Would it be better for me to continue the softer voice (my voice isn't deep anyway) or just speak with an American accent? Would it be easier Japanese people to understand me if I did that accent or would they just laugh if they heard me trying to imitate it? Please post. Thanks.