Most good stories start with a fundamental list of ingredients: the initial situation, conflict, complication, climax, suspense, denouement, and conclusion. Great writers sometimes shake up the recipe and add some spice.
Many scholars identify My Ántonia as a modernist novel, which, among other things, means that it defies typical plot structures like the good old Classic Plot. To start, think about the way that this novel is structured. My Ántonia is more like a series of episodes or anecdotes than a continuous narrative. There's no big central, plot-based conflict. Rather, there are thematic conflicts (like the barriers immigrants face in the West, or Jim's passivity when it comes to Ántonia). Because of this, we can't identify a particular moment in the novel that serves as a climax, or a conflict, or a suspense stage. Instead, it's more useful to think about how Cather uses a unique, non-traditional structuring to tell her story.