(sarcasm flooding room...)
Throughtout the series, before any actual invasion, the results of the right now, continuing invasion across our borders plague us in the war effort due to many large scale terror attacks (from Islamics, Chinese and Azatland activists) that keep occurring.
Ultimately, the entire Homeland Security apparatus is re-organized (in the novels) to take advantage of the 80+ million armed Americans and their second amendment rights whoi are organized into Home Guard units to interdict terror as it occurs.
Best to you.