In addition to the reasons others have given (self-sufficiency, and it being too late this time), closed boarders as a general and ongoing solution is very brit

In addition to the reasons others have given (self-sufficiency, and it being too late this time), closed boarders as a general and ongoing solution is very brittle. All it takes is one infected person to get across the border and you have no defence-in-depth. As a short-term measure in combination with other public health efforts, it might have some merit, but thats all really.