"That's still ridiculous. There's no way Al Qaeda has more than a few dozen actual operatives in the US, plus a couple hundred or so sympathizers capable of logistical support (i.e. fundraising)."
You say this while our borders are known to be wide open? I hope you are correct, but until the borders are closed, I will remain very nervous.
I don't think al-Qaeda has 5,000 operatives worldwide--from what I've read, they subscribe to the notion that three can keep a secret if two of them are dead, and they tend to recruit people they've personally known for years/decades.