A similar movement has a long history in New York State. If you ask people from New York State where they are from, New Yorkers who don’t live in New York City will reply, “Upstate New York”. They don’t want to be associated with city folk. The city folk will reply simply, “New York”. Long Islanders will always answer, “Long Island” or as they would say in their native tongue, “lawn-GUY-land!”
Staten Island has long desired to be separated from New York City. It is one of the five boroughs of New York City even though it is separated from the city by New York Bay. It’s also separated from New Jersey by the Arthur Kill and the Kill Van Kull (whatever a Kill and a Kull are. Might be Klingon?). Residents there feel that they have been neglected by the city government in budget and other matters. It is sometimes called the "the forgotten borough" by inhabitants. During the 1980s, there was a movement led by a Senator to secede from NYC. In a 1993 referendum, 65% voted in favor of it, but the move was blocked in the State Assembly.
Since New York State is already divided, it makes sense to split it into three parts; New York City, Long Island and Upstate New York (or Greater New York, or simply Not New York City). Staten Island would have the option of joining NYC, Upstate New York or New Jersey.
Michigan is another divided state. There’s the Lower Peninsula and the Upper Peninsula. They’re separated by Lake Michigan on one side of the Straits of Mackinac and Lake Huron on the other side of the straits. The Upper Peninsula borders Wisconsin. The Upper folks don’t associate with the Lower folks. In fact, they probably have more in common with Canada. This is a state that is already split. It could split to form the States of Upper Michigan and Lower Michigan, or like the Dakotas, North Michigan and South Michigan.
Other states exist divided. The Rocky Mountain Range divides the States of Colorado, Wyoming and Montana. Wyoming and Colorado are divided neatly in half while the Rockies claim one third of Montana. The eastern sides are part of the Great Plain which is the prairie, steppe, and grassland that lies west of the Mississippi River and east of the Rocky Mountains. The plain folks don’t want to associate with mountain folks. Since these three states exist divided already, it makes better sense to split them into two or three new states. The portions that include the Rockies would become the Rocky Mountain State (or Rocky Mountain High). The eastern sides would become the Great Plains State.
In terms of population, Wyoming has the least at 600,000 people (not including livestock). Montana has 1 million people, while Colorado has 5.7 million. An argument could be made to combine eastern Wyoming and Montana, letting eastern Colorado remain separate as the Stare of Colorado.
All these splits would really mess up the flag. We could have as many as 63 stars. What the hell, let’s throw in Puerto Rico and Guam for an even 65.