One, there are a few counties on Oregon that want to redraw the boundary so that they become part of Idaho. This, I think, is only mildly serious.
The second is the border of Indiana and Illinois, which is serious enough that the Indiana state legislature has voted to create a commission to work on it. It was a bipartisan vote, too. Because there are a number of rural counties in Illinois that would like to join Indiana, and two urban counties in Indiana that say if the option is on the table they’d rather be part of Illinois. Such a thing would need both states to agree and then send it on to Congress, but ultimately I don’t think anything will come of it.
When you look at state funding, these urban counties are sending more tax dollars to their respective state capitols than the states are spending in their counties. In the case of these rural Illinois counties, the state is spending between $5 and $6 per tax dollar collected. Does Indiana really want to take on such welfare queens? And give up some of their few donor counties in exchange? It seems hardly likely!
That’s the rub all across the US. The urbanized areas are subsidizing the rural areas. Are the rural areas prepared to do without such subsidies? They can say “the cities can’t live without the food we grow”, but the entirety of human history shows that the cities always come out ahead in these transactions.