This may have already been covered but the simple matter of how patrol officers are armed in American cities most likely to be attacked Mumbai style may be of some import. Washington and New York are probably the two most likely targets. Several years ago I had contact with a D.C. officer and he told me they were armed only with a 9mm pistol. If a Mumbai style attack occurred in DC the first officers to respond would be patrol officers and with only pistols they may as well have a bag of rocks to throw. I know the SWAT types would show up but a lot of bad things could happen in the interval.

There are places where normal patrol officers all have AR-15s. That gives them the capability to do something effective right away.

I don't know how NYPD guys are armed.