"... unlike 'claret' which in the US can be made from anything ..."
The California clarets of which you write, Peter, may have been inspired, at least in part, by English clarets of the early to mid-nineteenth century.
A history and description of modern wines
, by Cyrus Redding, published 1833, pages 328-29:
"It cannot be denied that the wines of Bordeaux, called "claret" in this country, though not adulterated like the wines of Portugal, still suffer great injury before they are considered fit for the English market. It has been thought necessary to give the pure Bordeaux growths a resemblance to the wines of Portugal, in some respect, in consequence of the false taste which has been give by the use of legislated port, thus one mischief treads upon the heels of another. Bordeaux wine in England and in Bordeaux scarcely resemble each other. The merchants are obliged to "work" the wines before they are shipped, or, in other words, to mingle stronger wines with them, such as Hermitage, or Cahors, which is destructive almost wholly of the bouquet, colour, and aroma of the original wine. So much are the merchants sensible of this, that they are obliged to give perfume to the wine, thus mixed, by artificial means, such as orris root and similar things. Raspberry brandy is sometimes employed, in minute quantities, for the same purpose, and does very well as a substitute in England, though any Frenchman conversant with these wines would instantly discover the deception. The perfume is sensibly different from that given by nature. These operations cause the clarets of England to be wines justly denominated impure, though not injurious to the constitution. There is nothing in them which does not come from the grape. It is only encouraging a coarseness of taste, which, after all, is but matter of fancy, while wholesomer wines cannot be drank. When old, claret is apt to turn of brick-red colour; this arises solely from miningling it with more potent wine."
It must be noted, though, that there is a tradition of a purer form of California claret, indeed an American claret, very well established and honored still.
PS: I haven't yet found the second edition of Redding's book, but the OED quotes it as one of the cornerstones of its definition of "claret", and to similar effect:
1836 C. REDDING Hist. Mod. Wines iii. (ed. 2) 53: There is no pure wine in France like that which is designated claret in England. This wine is a mixture of Bordeaux with Benicarlo, or with some full wine of France. Clairet wines..signify those which are..rose-coloured.
The third edition of 1851
is at hand, and to similar import.