Are you assuming bias/opinion is one-dimensional and the "median American" stands for the Truth?
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Yes, of course NPR is more on the side of democrats than republicans.
But, it is very much pro-business, and often pro-war status quo ("right"). And, as I mentioned ("identity politics"), also very much pro-diversity in race/gender/etc. ("left").
So, IMHO, very much "centrist", not "left" (except on race/sex/gender).