re: "Defensive actions?"
There is a theory that we can defend ourselves against terrorists by simply tightening our borders enough to keep them out. Ironically, the people proposing this are usually those who are the most virulently opposed to anything that seriously interferes with the freedom of movement across our borders.
Most of us would be quite happy to let crappy little nations go to hell in their own way. After September 11th, that was no longer an option.