I think a lot of the confusion comes from using the phrase "American hefeweizen", which (in my opinion) should never be used. A hefeweizen is a cloudy wheat beer of German origin which contains a considerable amount of ester and phenolic fermentation character. An American wheat beer is nothing like a hefeweizen other than containing a substantial portion of wheat malt. It is generally crisp, clear and cleanly fermented.
OK, I'll get off the soapbox now...