But if the govt has an 'idea', we'd be 'better off' knowing where/what is expected. That way, the folks who live in that area would be on a 'higher awareness'. This generalized, and often, alerting seems to be desensitizing people.
I'm no expert, but I believe if there's another attack, it will come during 'business hours'. These animals want to have the MOST 'soft targets' taken out, when they hit.
I wouldn't live in a state of constant fear or such, too stressful. If you live in a city, make plans to stay with family/friends who live in the country, if TSHTF. Silly as it sounds, all those 'preps' for Y2K would be a good thing.
As for the 'over-reacting' or the 'forewarning' to the islame whackjobs....only God knows. Stay in prayer, stay vigilant.