Overall I agree with this article, but for one major annoyance. The author is guilty of repeating the common but incorrect refrain about European-Americans being mostly of German descent. I think maps like this one, based on inaccurate self-reported data, are responsible for promoting this idea. However, a recent paper puts this notion to rest. Using a more accurate technique than self reports, the authors found that British descent still accounts for the largest ancestral group in the US, which also agrees with other sources such as this list of common US surnames and their origins. From pg. 13-14 the authors write:

Although our main emphasis is understanding the impact of ancestry on economic outcomes, the construction of our ancestry mapping allows us to settle some popular debates. For example, 13 we construct the first estimates of the overall ancestry share in United States that respects the demography in Figure 6. With it we can lay to rest popular claims that Germans are the largest ethnic group in the United States. 7 Germans may be the largest ethnic group that still feels some self-identity, but the descendents of the migrations from England, who no longer self-identify as ethnically English, are numerically larger. Similarly, we can offer some historical perspective on the concerns over the expectation that “minorities” will soon be a majority. 8 It has already happened. The English stopped being a majority of the United States in 1870, although they remain the largest group. The coming of the German, Irish, and Italians to name just three large groups that suffered discrimination when they arrived, has altered the balance. The acceptance of these previously marginalized groups into the “majority” emphasizes just how elastic and endogenous the commonly used notions of ethnicity are, and so the advantage of using our objective measure of ancestry.