I would think it is about both, foreign and domestic.

I mean, yeah we should probably be more afraid of foreign enemies, but look at what happened to Germany in the 30's. That was a domestic threat (to them) that they allowed to snowball into a world threat.

It reminds me of that (often paraphrased) quote by George Santayana, "Those who cannot remember the past are condemned to repeat it.*"

It really can happen here, too.

*Note:

This famous statement has produced many paraphrases and variants:

• Those who cannot learn from history are doomed to repeat it.

• Those who do not remember their past are condemned to repeat their mistakes.

• Those who do not read history are doomed to repeat it.

• Those who fail to learn from the mistakes of their predecessors are destined to repeat them.

• Those who do not know history's mistakes are doomed to repeat them.

I know wikis aren't the most reliable source of informarion but this entry about George Santayana has a lot of great quotes from him and is worth a read.