You read that right. He actually said 'but still'. Um. But still what?
And besides, Miranda has NOTHING WHATSOEVER to do with citizenship. It has to do with being in America. Land of the free, home of the brave, remember? Everyone gets Mirandized--white collar criminals and Mafia hit men and serial killers and kids caught with half a joint on them and axe murderers and child rapists and Bernie Madoff--because this is America. What part of "due process" does Rep. King not understand? If a suspect isn't Mirandized, it's entirely possible that s/he will be able to cry foul and walk away.
And the answer is yes, they did Mirandize Faisal Shahzad, after first questioning him under the public safety clause that allows for delaying Miranda. And he talked, before and after.
Source is here.