That's simply not true. A larger police force translates to more comprehensive law enforcement. If it doesn't, then there's a systemic failure in the way police are run (and we have plenty of examples of those too). Of course "more police" isn't the only way to increase the effectiveness of policing, but it does help.
The security theater was specifically about TSA and other untrained (or minimally trained) symbolic gestures. Actual policing is not theater.