(CNN) In the past week I have seen flowers and candles carpeting a street in Munich , the tranquility of a small Bavarian town shattered by a suicide bomb and a small church in suburban France sealed off after its octogenarian priest had his throat cut .

Before these horrific events, there was a knife-wielding teenager on a German train . And before that, much deadlier attacks in Nice Brussels and last November, in Paris.

This year has seen an accelerating pattern of attacks linked to ISIS in Europe and beyond -- from Turkey to Bangladesh , the United States to Indonesia. According to the group IntelCenter, which tracks acts of terrorism, there has been a significant attack directed or inspired by ISIS every 84 hours since June 8 in cities outside the war zones in Iraq, Syria, Sinai in Egypt and Libya. CNN's own tracking of attacks supports that conclusion.

More than half of those attacks have been beyond big cities in places "not traditionally under threat of terrorist attacks," says IntelCenter. This rash of random, low-tech but deadly attacks has fueled public unease in Europe and eroded faith in governments to tackle the threat of terrorism or discern who might turn to violence.

It has also diminished trust in justice systems accused of leaving too many dangerous people at large. Despite twice trying to go to Syria, Adel Kermiche -- one of the 19-year-old attackers who killed the priest in France -- was released from custody and allowed out of his home for four hours a day. Despite repeated efforts to deport him, the Ansbach bomber -- Daleel Mohammad -- was still in Germany.

In my week-long journey across Northern Europe, that public unease was never far from the surface. Callers to German radio stations said they were apprehensive of visiting a mall. A shaken teacher who knew one of the attackers in France told CNN: "I never thought for a day in my life that a young person would commit a terrorist act here in Saint-Étienne-du-Rouvray."

In Ansbach, a picturesque town in Bavaria, stunned locals drifted past the scene of the suicide bombing at a café, where abandoned drinks and playing cards bore silent witness to the moment of terror the night before.

These attacks have also prompted fundamental social questions. Respect for openness, liberal democracy and due process are being eaten away by a toxic mixture of extremism and psychosis.

Fear breeds civic distrust

Intelligence analysts Flashpoint Partners say there is "more coordination between potential lone actors or small unofficial cells with jihadi media -- a way to guarantee that their message is disseminated and to prove their allegiance to ISIS without necessarily joining its ranks."

The consistent public message from ISIS over the past year or so has been: "Don't come to Syria; kill the unbelievers at home."

These attacks, and the expectation of more, have fed not only the mood of growing anxiety. They have become part of a combustible political debate. I witnessed this in its rawest form at the site of the Munich killings. A young relative of one of the Turkish victims called out "Allahu Akhbar" in prayer, which was met by a torrent of abuse from some right-wingers present, provoking the Turks to yell "Your sisters will be next." Police moved in swiftly to keep the two groups apart.

In a poll after the attack in Nice, more than two-thirds of the French people questioned said they did not trust the government to combat terrorism effectively, a sharp increase over the previous year. Prime Minister Manuel Valls was booed by some of the crowd when he attended a memorial service for the victims.

JUST WATCHED French resort town reels from terror attack Replay More Videos ... MUST WATCH French resort town reels from terror attack 01:36

"The government will have to answer the question: how flagged individuals, including one under judiciary control for attempting to wage jihad in Syria, were let free to commit such attacks?" asked former French President Nicolas Sarkozy, widely thought to be eying another bid for the top job next year.

France has deployed 4,000 troops in Paris; another 6,000 beyond. Bavarian Premier Horst Seehofer has called for similar measures in Germany.

But it seems even 100,000 troops could not guard against these random attacks.

The answer, to Sarkozy and others on the right, is internment without trial for anyone suspected of jihadist sympathies. It would be a dramatic departure from the cherished tradition of due process, but according to recent polls conducted for Le Figaro, such a move has the support of at least three-quarters of French citizens.

Is EU migration really linked to escalating terror?

JUST WATCHED Many Germans no longer want migrants in their country Replay More Videos ... MUST WATCH Many Germans no longer want migrants in their country 02:19

The outbreak of terror attacks in Northern Europe has also translated into growing hostility toward migration. German Interior Minister Thomas de Maziere pointed out that none of the recent attacks in Germany had been carried out by refugees who arrived last year. Nor was the attack in France. But that has not changed a perception among some that the tide of mass migration will end badly. The far-right Alternative fuer Deutschland party is polling at some 20% in Chancellor Angela Merkel's home state of Mecklenburg ahead of state elections in September.

Merkel has again insisted that "we can manage" the influx and integrate refugees into German society. A year ago her decision not to send would-be migrants back to their first point of entry into Europe led tens of thousands -- from Syria, Iraq and elsewhere -- to head for Germany. The slogan "Refugees Welcome" was on banners at city halls and football matches across Germany. It was a remarkable display of generosity toward those fleeing violence and persecution.

But the welcome has worn thin. Merkel is on the defensive . She -- like French President François Hollande -- must face the voters next year if she wants another term. Some within her own coalition now cry "We told you so" -- among them Bavarian Premier Seehofer.

Merkel has promised more decisive action to deport those whose requests fail and better detection of those becoming radicalized.

But the scale of the problem is enormous. According to German government statistics from March, about 400,000 asylum applications were still being processed. But half of those whose requests had been rejected -- nearly 170,000 people -- were still in Germany, among them Daleel Mohammad.

And sociologist Armin Nassehi, who examines migration issues at Ludwig Maximilian University in Munich, says many young male migrants are more vulnerable than most to manipulation or emotional instability.

"The central problem is that refugees have much more complicated life situations. They are people with traumatic experiences on the one hand and not knowing what will happen them to the future on the other," he told CNN.

Hard choices ahead

The core of the issue is this: how much is Europe prepared to compromise its way of life -- the freedoms and rights taken for granted for generations -- to do battle with random terrorism? How many public places become fortresses? How many events are canceled (as the French interior minister has recommended) if adequate security cannot be guaranteed? How much must be spent on the militarization of policing? And how many powers of arrest and detention should a government possess without reference to the courts? The state of emergency in France declared last November is set to run another three months at least.

As she visited the site of a makeshift memorial outside city hall in Saint-Étienne-du-Rouvray on Wednesday, 23-year-old Meggy Simane paused for thought.

"It's a problem for everyone," she said, "the gay community amongst us, the Jewish communities, all walks of life. We are all different with our own cultures but at the same time we are all the same."

A 19-year old who lived just a few streets away from Meggy thought very differently.