Does this concern anyone that if a flag good be place, why not a bomb or something else? Does this show how weak we are? Are we a sitting duck for another attack?

This only lends credibility to the idea that “safety” is largely an illusion meant to comfort people more than anything. The fact that terrorist attacks are so rare isn’t because we have safety measures in place to prevent them; nothing is really stopping anyone from going on a murderous rampage other than a general consensus that that is a deplorable thing to do.

We are continuously shown how easy it is for someone to go into a school and shoot innocent kids, or park an explosive filled van next to a building and blow it up. Law enforcement cannot be at every place at every time, and security measures can be sidestepped in many ways.

The only sign of weakness is our overwhelming ability to be deluded by such illusions. A locked door only keeps a decent man out, thinking otherwise leaves you vulnerable. That locked door won’t stop someone who wants to get in your home, the reason it doesn’t happen very often is simply a testament to the amount of decency in the population.

On another note, considering us as “a sitting duck for another attack,” is just as ludicrous. Terrorism isn’t as prevalent as the media makes it out to be and neither is violent crime for that matter. Living in fear of such things is just as deluded as thinking you’re safe from them.

Prank,

No terrorist is going to expose their plan nor try to deflect interest in their real plan by creating a distraction. Terrorists don't ever want to bring any attenton to themselves because the best way for their plan to work is surprise. Therefore, I do not believe that this was a test of security or "Dry Run" to see if they could get away with it, but simply a prank.

Most likely just a prank. But no matter what it was, it wouldn't show that we are a sitting duck for another attack. What are we supposed to do, assign a major security team to every bridge in America? People need to stop complaining about certain security measures, people will always be able to do terrible things no matter what.

Are we a sitting duck for another attack?

Always. Terrorism isn't near as extreme as it is in Europe, but we are always sitting ducks. Terrorism has existed since the beginning of time and it will always exist sadly.