Don't make me laugh. The American border control is extremely ineffective. Check this:
http://www.breitbart.com/Breitbart-Texas/2014/09/8/OKeefe-Brings-Attention-To-Porous-Open-US-Northern-Border
http://www.dailymail.co.uk/news/article-2747965/I-ve-never-seen-Border-Patrol-Filmmaker-shows-Ebola-infected-ISIS-terrorist-sneak-Lake-Erie-Canada-Cleveland-RICIN-Rock-Roll-Hall-Fame.html
James O'Keefe has shown that anyone can cross the American border. The ISIS terrorists are no exception. If the technologically inferior Mexican drug cartels can move their men across the border with ease, what prevents the ISIS from sending its men across the American border?
Sure you can't prevent everyone from sneaking in through the border unless the US builds some massive apartheid wall like Israel. My point is that it's extremely unlikely another 911 could be carried out by groups like ISIS. Bombing them like the West is currently doing will only create more terrorists in the future.