European Terrorist Alert

There have been armed military and police in French train stations, airports and tourist sites, especially in Paris, for almost two weeks now. The alert here in Europe was given after the first bomb scare at the Eiffel Tower. Tourists and workers were evacuated and the entire area was searched for an explosive device. None was found. The same thing has since happened at a very busy Paris train station and again at the Eiffel Tower.  Britain published an alert at almost the same time, as did Germany. It seems that the threat is directed principally at France and Germany.
European news media are reporting that telephone taps have led to two Britains and six Germans, all of whom they say are in Pakistan along the Afghanistan border. That was the reason given for the US military drone attack into Pakistan several days ago. One of the Britains was allegedly killed.
And now the United States State Department is advising all Americans to be careful when traveling in Europe and to avoid tourist sites. 
I haven't heard of any special alert status for the USA, but I suppose there is one.
I was in Europe the last time such an American alert was given for US travelers in Europe. It was in 1991, as the first Iraq war began. People were panicked and fled Europe like lemmings.
This time its feels very different. The French government says it has the situation under control. The Germans are quiet. Britain is advising its citizens living or traveling in continental Europe to be careful and watch for anomalies. Americans interviewed on the streets of Paris are smiling and saying the alert won't affect their plans at all, while military patrols dressed in camouflage gear and carrying what look like semi-automatic weapons are circling behind them.
It seems we've become used to terrorist threats over the last 15 years. That could make it a lot easier for the terrorists to strike. I hope we don't become too blasé.