Do federal agents/cops have to ask TSA or Airport police to enter an airport armed in an emergency?
Essentially Federal Agents outrank everyone else and, unless the situation is something that can be predicted well in advance and a call for alert can be prepared and go out in time, the Agents will just come on the scene and take over. They can order TSA to do what they need them to, though normally they will go through the boss who will order his or her own people. Agents running through a terminal with drawn guns may look dramtatic on screen, but the only time it might happen is if lives were in immediate danger. The Agents (plain clothed) may well be in greater danger from Sky Marshals if they did that without advance notice. Normally, the boss would see the boss and have things done where and when the public would not see it. If it comes to the point where running with guns is needed, my advice is to hit the deck and worry about procedures when it is over.
What are your views on guns in the united states?
I saw a movie once where only the government and police had guns. It was called Schindler's List. Didn't end well for the unarmed citizens . . . Luckily, whether or not people should have guns and be able to defend themselves has already been decided here in the United States. It's a constitutional right.