As long as you cut a hole in the middle: Texas + Oklahoma + Kansas + Nebraska + South Dakota + North Dakota, you can easily bankrupt the coasts. Just put a no fly zone over the whole area and charge ludicrously high land crossing taxes. Force them to either use expensive air travel that goes the long way round or heavily taxed ground travel. Shipping anything from one coast to the other would become extremely expensive, giving coasts a massive disadvantage in trade and a massive advantage to the newly formed union. Nearby states would join quickly. Those that refuse at first will fall once bankrupt, and the more states join the faster others go broke. All you need is a big beautiful wall in the middle. Walls work.