‘Twin communities’ (communities that were split up by the imposition of the international border) should be united through the creation of a political enclave that encompasses a small territory (such as a town or small city) on both sides of the border. These enclaves would allow, for example, Americans and Mexicans to cross the true international border with little or no restrictions to do business with people or visit relatives on the other side, or just to travel around. The perimeters of these free crossing zones would be completely surrounded with an impervious boundary and lined with checkpoints. It is these perimeter boundaries that would take on the full responsibilities associated with the true international border. Essentially, all people within these enclaves, even American citizens residing on the American side of the true international border, but on the inside of these special enclaves, would need to go through a full customs search before they are allowed to enter the US mainland through one of the perimeter checkpoints. However, US citizens within these enclaves need not apply for a travel visa or any other entry related documentation that is not required of regular American citizens.
These special enclaves would need to have their own emergency vehicles because vehicles from the mainland will not be able to get through the perimeter border quickly, due to security checks, etc.
Taxes would be collected and funds would be distributed in the same way as before, with the true international border being relevant for tax purposes. If needed, there may possibly be a small additional tax on businesses and all people living within the enclave to make such a setup financially self-sufficient.
The above model should be used around the world because many countries have far more seriously disrupted ‘twin communities’ than does the United States.