This is not so true...lets look at for example the difference between the North East, the souththwst, the midwest, Hawaii and the "south" (which i have lived in each of these regons)
the southwest has primeraly a Mexican and centrel american influence where as lets say Hawaii has a huge Japanese and Chinese influence. in the south we can find people speeking French because of the cagons(which has French roots)as well as the remonats of the old plantatins.also in the south we can find a strong and very traditianal Black comunitys. the midwest is very much farming comuitys, even in the larger citys we can see this infuence.
hell... Hawaii and Texas where bolth at one point its own country! the contrast in "culture" within the US is profound if you have the eye to make the distinction, so to say that the culture dosent change much frome place to place is ubserd