An American in Paris culminates in Jerry's fantastic dream sequence set to the "An American in Paris" suite by George Gershwin. Jerry stands on the balcony at the art students' ball, watches Lise drive off with Henri, and then spends the next 17 minutes imagining himself and the girl who got away dancing through a series of living French paintings. It's lavish, it's lengthy, and it's totally out there.
What's the point? The dream ballet sequence reflects the fantasy world that Jerry lives in. In short, it's how he justifies his dreams of being an awesome artist. In reality, he's struggling to get by and lacks the drive to achieve his goals. In his dream sequence, he doesn't dream of being a great painter; he puts himself in the masterpieces of others. He doesn't create art; he inhabits it. Or, put another way, he doesn't make art; he is art.
The An American in Paris Ballet is also how Jerry works out his grief over losing Lise to Henri. Simply put, he dances through his pain and turns it into art. Kinda makes you wonder why Jerry doesn't just hang up his paintbrushes and pursue a career as a hoofer, doesn't it? He may be a thoroughly mediocre painter, but in both fantasy and reality, he's one heck of a dancer.
Now, we know what you're thinking: "But Shmoop—that's the not the end! The end is when Lise comes back!" Fair point, though there's no need for you to yell. Here's the thing: given the immensity and artistry of the ballet, the fact that Lise returns is practically a postscript. Her return has nothing to do with the lengthy ballet that precedes it. It's not like her Spidey-sense starts tingling in the car and she tells Henri that they have to go back because Jerry's having a nutso dream about her.
What we're saying is, the ending is kind of weird, but, if nothing else, the one-two punch of Jerry's dream and Lise's decision to choose Jerry suggests that maybe Jerry's started to figure things out. Maybe by inhabiting art and getting the girl, Jerry's ready to strap on his smock and really make a go at painting on his own (because we're willing to bet that sponsorship deal with Milo is, like, so over). Maybe, after witnessing Henri's selfless nobility, he's ready to stop being such a cad, too.
In short, after a dramatic night at the masquerade ball that leaves loose ends untied (What if Henri comes back? What if indecisive Lise changes her mind again? Did Milo ever get her second drink, and what if she wants revenge?), Jerry's future is uncertain at the end of An American in Paris. We won't know for sure how his life, love, and art pan out unless MGM decides to release An American in Paris 2: Parisian Boogaloo.