Pronunciation of foreign words in American vs. British English

One of the differences between modern US English (hereafter referred to as "American English") and British English is the way in which we pronounce foreign words, particularly those of French origin and/or related to food. For example, Americans…

• drop the "h" on "herb" and "Beethoven";
• rhyme "fillet" and "valet" with "parlay" as opposed to "skillet"; and
• pronounce foods like paella as /paɪˈeɪə/ (approximating a Castilian or Mexican accent), whereas the British pronounce it as /pʌɪˈɛlə/.

In general, the British seem to pronounce foreign/loan words as they would be phonetically pronounced if they were English, whereas Americans tend to approximate the original pronunciation.  I've heard some people claim that this trend is due to the melting pot nature of America, and others claim that the French pronunciation, in particular, is due to America's very close relations with France during its infancy.  This latter hypothesis, however, seems to be contradicted by the following:

Avoid the habit of employing French words in English conversation; it is in extremely bad taste to be always employing such expressions as ci-devant, soi-disant, en masse, couleur de rose, etc. Do not salute your acquaintances with bon jour, nor reply to every proposition, volontiers. In speaking of French cities and towns, it is a mark of refinement in education to pronounce them rigidly according to English rules of speech. Mr. Fox, the best French scholar, and one of the best bred men in England, always sounded the x in Bourdeaux, and the s in Calais, and on all occasions pronounced such names just as they are written.

I wondered: At what point did the USA drop the apparent British convention of pronouncing foreign words as they are spelled?

I asked this question on English.sx, to little fanfare; most people—including Peter Shor!!!1—had trouble accepting that this phenomena even exists.  Therefore, I extend my question to the Blogosphere!

I did some more digging, and it is interesting to note that there seems to be a trend in "upper-class" (U) English to substitute words that have an obvious counterpart in French with words that are either of Germanic origin or those that do not have a direct equivalent in modern French.  For example, in U English:

• scent is preferred over perfume;
• looking glass is preferable to mirror;
• false teeth is preferable to dentures;
• graveyard > cemetery;
• napkin > serviette;
• lavatory > toilet;
• drawing-room > lounge;
• bus > coach;
• stay > corset;
• jam > preserve;
• lunch > dinner (for a midday meal); and
• what? > pardon?

This is admittedly a stretch, but perhaps there is some connection between the US's lack (and some might say derision) of a noble class and its preference toward non-U/French pronunciation?