It's fair to say that—on a very basic level—"Evangeline" is a poem that's all about setting. Think about it: we start off in the beautiful, idyllic setting of Acadia:
IN the Acadian land, on the shores of the Basin of Minas,
Distant, secluded, still, the little village of Grand-Pré
Lay in the fruitful valley. Vast meadows stretched to the eastward,
Giving the village its name, and pasture to flocks without number. (20-23)
As a farming community, we see how the locals there are very much rooted to their land (check out "Symbols, Imagery, and Wordplay" for more on that). And for that reason, their exile at the hands of those mean ol' English is made even more terrible. They have to leave this wonderful Canadian Eden in search of a new home.
Eventually, though, the Acadians (some of them anyway) seem to find a setting that's somehow even better than their homeland. Check out what Basil the Herdsman has to say about it:
Welcome once more to a home, that is better perchance than the old one!
Here no hungry winter congeals our blood like the rivers;
Here no stony ground provokes the wrath of the farmer.
Smoothly the ploughshare runs through the soil, as a keel through the water.
All the year round the orange-groves are in blossom; and grass grows
More in a single night than a whole Canadian summer. (986-991)
So, it's a big win for the Acadians then? Well… not exactly—they may have gotten an upgrade in setting, but it's important to note that not everyone was able to make it down to Louisiana, and those that did were had to endure no small amount of hardships before the arrived. And, don't forget about that pesky fever that affects folks down there. Not even a spider in a nutshell can cure it (1006).
A fever is the least of Evangeline's worries, though. Driven by her search for Gabriel, she's not able to resettle in this new setting. She moves on to the Ozark Mountains, then up to Michigan, and finally to Philadelphia. That's logging some serious miles, even by today's travel standards. Now imagine making that voyage by horse, or on foot.
Evangeline's shifting settings reinforce the tragedy that has befallen her. She's literally lost and out of place. No matter where she finds shelter, she's never at home. And home, in this poem, is the most important setting there is.