Owen Wister 
A Straight Deal; Or, The Ancient Grudge [PDF ebook] 

This is a polemic (or series of polemics) written to make Americans less hostile toward the British before and after the US entered World War I on their side. The author does his best (which is pretty good) to explain (away) contemporary British customs Americans might find offensive. (No balance – the Germans are heathens or worse in his book.) As such it's a window more into British than American ways: author says British reticence is a big turn-off. What a British subject of 1918 would say about Page Three girls and lager louts (Wister points to American "coarseness") does not bear thinking about.
Best part is in the first chapter, where a correspondent tells Wister what it would take for Americans to get along with the British: have a bigger navy. Accurate, that.
A striking presentation of facts about the British Empire, a plea for a better understanding of the English by Americans and a powerful argument for Anglo-American friendship.