Why does everybody assume the division will be physical rather than spiritual or ethnic
A series of assassinations of certain black and Hispanic leaders, coupled with some bombing operations by Black Muslims in malls crowded with Christmas shoppers would do quite a bit toward "dividing" the US into three parts (white, black, and brown)
Evidently,the Nazis like the black Muslims and separatist Mexicans because they all want to split the U.S. into different ethnic enclaves and territories.(After the split,the Nazis could "clean" one smaller area at a time,eventually having a white continent.)
The Nazis and Islamists both see the Jewish people and their friends as targets.
Also,I've noticed a number of internet sites run by the tree and bunny huggers that support the Palestinian and other "Muslim" causes.
The terrorists could try to use our own "diversity" against us.