American speaking Russian is quite rare phenomenon. American speaking grammatically correct Russian is very-very rare phenomenon. So I can say more or less what is heavy American accent in Russian but have no idea what is light American accent.
As for me, the very sound of (heavy) American accent do not make any special emotions.
Of course, if a person pronounces learned phrases without understanding meanings of separate words (parrot speech, like in Hollywood movies), that is hardly comprehensible and sounds both extremely weird and funny.