I was discussing this with a couple of my officers tonight. My theory is that these kinds of attacks are so rare in the US because of the number of citizens that are either armed or have quick access to a firearm. If you notice, the majority of the "terror" attacks have occurred in California and New York (NYC) to be exact, two places that have very few citizens (other than the police) carrying firearms or having quick access to a firearm. I would like to think that if something similar to what happened in London were to happen in Indianapolis that there would be a more significant armed response from the citizenry because of our right to carry. I hope it never happens here, but if it does I hope that I am proven right.
Garland, Texas is a prime example.