For a movie lover, this is soooooo hard! I think all such lists are. I like what Lindsay did with it (not for the first time).
To the unintiated, this is a list of 10 movies that could serve as a primer on America (i.e., the USA) to a visiting alien or some hermit who had, for personal reasons, missed the last 100 years of popular culture I've let it simmer for a few days and I'm still pretty happy with it, though there are personal favorites and movies I rate higher aesthetically that aren't on it. There is no particular order, and notes will follow.
The Lady Eve
Bonnie & Clyde
From Here to Eternity
Casualties of War
McCabe & Mrs. Miller
Long Day's Journey into Night
I link to each through IMDb as a default.
What would I hope my hypothetical innocent would take away from this list? First, I suppose, is that we are not a simple (at least not in the sense that our current leaders want us to be) people. We can laugh at very serious things, without not taking them seriously. We make up our beauty on the fly (and conceal the hard work). We prefer to tell the truth. We worry about where we came from, we're anxious about class (and are uncomfortable talking about it), we will gamble on the future (and know we might lose - i.e., we're essentially optimists).
And there's nothing monumental or triumphant about any of these movies, and that may be a flaw in the list, but I think it is closer to the American grain than the chest-thumping that's going on now, and why that will not last. We're just too revolting, and that's what I love about us.