The late Queen was half Scot, the present King has English, Scottish, Danish, Russian and some German ancestry.
The present King’s most recent ancestor born in Germany was HRH The Prince Consort, Queen Victoria’s husband, who left Saxe-Coburg-Gotha in 1840.
Given logic of your argument, and the rate of German immigration to the US, you would have to argue that 50 million Americans are really Germans not Americans.
In other words, it’s a dumb argument.
Germans are the largest ethnic group.
English are not, because a lot that were counted as English were actually Irish, Scots and Welsh.