Most of the reviews already posted recommend against this film. I thought I'd chime in with the supporters.
Of the 8 films in the Warner Archive "Robert Montgomery Collection" bundle, this is my favorite, followed closely by Faithless (1932). Overall, I've rated 18 of his films, and gave 4 sevens, 9 sixes, 4 fives and 1 four. That fits my overall rating profile pretty well, except one should have been an 8 instead of a four or five. So I'm not a special fan of Montgomery.
I agree that Montgomery's portrayal here is heavy-handed. His character, the titular Earl of Chicago, talks and behaves like a cross between Huntz Hall and Leo Gorcey, with an annoying giggle to guild the dandy-lion. Oh, and leave us not omit the Cagney-esque shoulder-roll.
The Earl has a twist that is interesting, if unlikely for a Chicago bootlegger: he's gun-averse, to the point of breaking out in a sweat when he sees one in some circumstances. He's volatile and sadistic, as demonstrated by his ring-slapping a man who displays his gun "for a laugh." He happily pays his thugs overtime for after-hours physical intimidation of a customer who withdrew his business during these post-Prohibition days. (We don't get a fix on the year, but it must be close to the repeal of Prohibition in 1934, because his cousin Master Gerald is about 13 during the flashback (the actor was 15), but is with his regiment in France in the present-day of the movie, late 1939.)
The Earl learns and grows during the story. He is humbled by the grandeur of the House of Lords. He discovers history, both English and American. He learns the basics of the culture of the landed gentry and their tenants, particularly about noblesse oblige. Edmund Gwenn delivers his usual pleasurable and effective performance, helping to shepherd the American Earl through his discoveries.
Unless this print was politically enhanced for later re-release, this film was released in January 1940, in the middle of the Phoney War. Hitler invaded Poland September 1, 1939, and Britain, France, Australia and New Zealand declared war on Germany 2 days later. America declared its neutrality 2 days after that. Europe languished in the Phoney War until Hitler invaded France, Belgium, Luxembourg and the Netherlands in May 1940, although the Nazis began with other aggressions in March and April. (The History Place has a nice timeline, easily found by searching for "hitler's invasion of europe.")
Because the visitors to the castle in 1939 are mostly in uniform (not true during the flashback to 1934), and English troops in France are mentioned, I interpret part of the film's intent was to reduce America's isolationism, implying that it was OUR noblesse oblige to help defend Europe, especially England, against Hitler's aggression. The message is subtle, but I see it. MGM got more much overt about our noblesse oblige in 1940 with films Escape and The Mortal Storm.
The film's revenge plot line involves Edward Arnold's character (also delivered with his customary skill). One of the effective aspects of the film is that this character is written and performed to throw us off the scent. While we see his secret vengeful actions, he also interacts with the Earl and others beyond the need to disguise his intent. I wondered whether his actions were as destructive as they seemed.
MGM does its usual excellent job of providing beautifully designed and dressed sets.
I liked this movie. I only give a rating of 7+ if I recommend the film.