I don't know how much I can add, but will reply anyways, as an American who has an interest in these things (and has visited the landing site and the cemetaries and monuments found there). Some random points.
1) Most Americans know very little of WWI. Even if they had heard of "Trench warfare" I doubt they would know what countries the trenches (or western front) were in.
2) Wizards sells books in other countries. The same books. Including England, Australia and New Zealand (and I have seen some in Turkey, through a local distributor).
3) Galipoli is the battle for Turkey and the Anzacs. It is well known in England (as far as these things go), if not as famous as the Somme. General histories of the war, published on both sides of the Atlantic, often give it quite a bit of emphasis. Both for its strategic implications (failure to relieve the Russians and defeat of the British Empire by a non-western European power) but also becuase it is different, and breaks of up the monotony of the western front. The few television series on WWI also give a fair amount of coverage
3.5) It is hard to imagine any student of WWI, even casual ones, not seeing mention of it.
4) It was a bone headed analogy. Trench figthing on the western front is not a proper comparison to individual battles (it would be comporable to "Tank warfare", "submarine warfare", "dogfighting" etc). And Gallipoli is one of the best known battles of a largely forgotten war. There are litterly thousands of battles that could have been chosen instead.