Stealing from the "Jews go to America instead of Israel" idea, and the idea that Wyoming and Montana were heavily settled by post-WWII Jews, I'm wondering if perhaps other similarly troubled minorities in the US might take a look at Utah (it was a long time ago, sure, but point of the matter is, the Mormons didn't like how things were going, and went out to a place where they would become the majority), and Wyoming and Montana, and decide that if those people could take a lightly-settled place, and immigrate in great enough numbers that they became the majority, then so could they themselves.
So what would be the effects of a Montana with about 2.5 million (974,989 in ours), North Dakota with about 1 million (646,844 in ours), Wyoming with about 1.5 million (544,270 in ours), and Idaho with about 3 million (1,545,801 in ours) in modern times.
Would there be any major changes to the infrastructure, beyond further urbanization? That is to say, could Idaho, say, remain that place where all the potatoes come from, with just as much (if not more) farming going on, or would the greater population push out a lot of the farms?