This was signed simply by someone called AnArmyVeteran and the title of the post is "What if the United States was attacked & occupied? What would you do?" There's more than I have quoted here and a quite a number of comments. You might want to go take a look.
What do you think would happen if another country invaded our country and occupied it with a huge number of soldiers? Do you think a lot of Americans would sit and do nothing regardless of why the foreign military was here? Or would a lot of Americans shoot at the occupying force?
I'm sure that if the US was occupied it would mobilize a lot of people to strike back at the foreign military. Hell, there are a lot of Americans who belong to militias who want to strike at their own government, so it seems like a given they would constantly attack any foreign occupiers. And ironically, that foreign military would call Americans 'insurgents'.
Imagine the leader of the occupying country saying he will keep his country's military in the US until all of the insurgents are rounded up or destroyed. This is virtually the same scenario we are facing in Afghanistan.