Travelers in the United States already have to deal with intrusive searches when traveling on commercial airlines. It would be extremely unfortunate if the police state were expanded to all places where Americans gather. It is unlikely that doing so would prevent an attack, which can happen quickly, and which can happen outside of secure zones. In addition, this would be at a monumental cost that Americans cannot afford.
The TSA is largely in place to make the American public feel more secure about airline travel in the wake of the September 11th attacks. In 2013, a man demonstrated that he was able to construct a bomb using only items that he purchased inside the airport beyond the TSA checkpoint. The TSA's record at stopping potential threats is spotty. It's not their fault. There really is no way to assure our safety, whether inside airports or otherwise.
Having the tsa at sporting events and music festivals is not protecting our freedoms it's intimidating the festival and sports goers by subjecting them to intense scrutiny and uncomfortable personal searches. The only reason why we tolerate it at airports is because people have used airplanes in the past as a means of mass distraction, how on earth would mass destruction be achieved at a football game with normal security measures in place (I.E. Medal detectors and police officers taking care of unruly fans). Would you take your son or daughter to their first baseball game if they had to get groped and frisked like a criminal? People are capable of being responsible, big government dose not need to waste our money on looking for terrorists at a Britney Spears concert