Can there be another American Revolution?

My son and I have become big fans of the TV series "Falling Skies" and we try not to miss an episode.  For those of you who have not seen it, I recommend that you take a look at it.  Its on Sunday evenings on TBS.   The show is about a band of people in Massachusetts that is trying to survive and destroy the invading aliens from another planet.  In the show they refer to "2nd Mass" (the second Massachusetts) and they carry on many of the traditions of the United States.  They carry flags and still say the pledge of allegiance.  

My thoughts today however wonder, "Will it take an alien invasion to bring that about?".  The US has been protected on both sides by 2 oceans and 2 countries on both sides that are militarily non-threats to its existence.   This strength has also been our weakness.  Strength, because we can build and grow as a nation without concerning ourselves about what will happen if we are attacked.  Weakness, because we can sleep at night that no invading army can seriously attack us, we have become complacent about our history and our way of life.