Yes, approximately 40 of "those people" managed to outwit the combined federal intelligence apparatus and law enforcement offices, some 50,000+ strong with funding of over $30 billion per year, and kill 3000 luckless Americans.
And just how do you then justify RP wanting to get rid of these agencies? Its easy to throw rhetoric like that around, but think first next time. Your post just managed to sum up that if RP becomes President and if he is able to get rid of the agencies he would like to, then the sky is the limit to the number of "those" (not sure why you put it in quotes, they are Al Qaeda) people who can attack us again.
Oh, but you say, that will never happen under RP, he will have immigration under control...yea, like a 25 foot fence surrounding the border and an economy based on the dollar backed by RP gold will stop determined jihadists from bombing us...
Those agencies, if anything, need to be beefed up...with proper funding, proper protocols with who knows what info, so we dont have a fuster cluck like last time, and allowed to stop the terrorists as they have in the past 7 years.
I dont care how you want to argue it, you need a good offense to prevent these type of attacks from happening again, albeit a war in Afghanistan, whatever, you cant just sit in your home and expect if you leave them alone they will go away.