Although I fully agree that we have such foreign enemies, I submit that the current threat to the consitution comes from within. If our constitution were strong in the hearts and minds of the people, and of our representatives, then those foreign enemies would have less power over us. The fact that the constitution is not currently respected, gives those foreign agents you mentioned the power to act.
Here is a scenario that is a subset of one of yours...
Obama, and the Democrats in congress, with their 60-vote majority, pass the "Fairness Doctrine", and "Net Neutrallity" laws, thus taking all their opponents off the air (and off the internet) - Rush Limbaugh, Shawn Hannity, Glenn Beck, Mark Levin, PJTV, Bob Basso (Thomas Paine on YouTube), Fox News, and our own web site, all gone!
And, of course, ABC, NBC, CBS, CNN, MSNBC would all be considered "fair" already, so the law wouldn't apply to them.
The only thing standing in their way now is the Supreme Court. How will they rule? The Supreme Court hasn't exactly been strong supporters of the First Amendment lately. They allowed the so-called "Campaign Finance Reform", and declared it constitutional, even though it says you cannot take out an add against a politician within 30 days of an election - a crystal clear violation of the First Amendment.
This act would be equivalent to the King preventing the publication of Thomas Paine's "Common Sense", in 1776.
I think that this scenario is very likely, with or without any other disaster.