Once again a high profile Islamic attack raises some crucial questions about Europe..

Key to understanding what is happening, and what is not happening, is a critical issue in the whole question of what has become of Europe since World War II.

As a result of US encouragement, and European frustration with its history of warfare, the European Union established a laudable framework of openness, and assurance of human rights.
At least to some degree, the value of protecting human life has had to compete as second in priority to the values of openness and human rights.
Americans of my generation grew up in war- and post-war years thinking of Europe as a dark and ugly place. Not a few of my correspondents still seem to think that the United States is a far superior place.
My own view, having set foot in all of the US States and all the countries of Western Europe (except for the tiny ones) is much different. European cities and public transportation have no reason to apologize before Americans. It is hard to find an indicator for economic welfare, health, environmental quality, consumer protection, education, or personal security where the US scores as high as the Western European norm.
None the less, there are problems in Europe. They include land connection to the Middle East, substantial Muslim communities already in place, more coming, and a resistance to ending the convenience of open borders without barriers of inspections. 
The most recent attack raises the question of controlling access to airports, which the Americans have shown is feasible. Controlling access to big city metro lines, where thousands stream into stations and onto trains every minute of peak travel hours defies the planners of public administration.
Until now, European officials have been willing to pay the price of occasional casualties instead of imposing what would be draconian controls. Nothing Europe has suffered to date matches the catastrophe of 9-11, and what it produced by way of program changes in the United States.
Those who think these problems are easy should consider the porous borders of the United States, and those between Israel and West Bank Palestinians. The shortfalls appear in estimates of 12 million illegal immigrants in the United States, with who knows how many more still coming over the Mexican border, and perhaps 20,000 West Bank Palestinians entering Israel daily, and illegally, for work, alongside some 180,000 with permits who come through established.entrances.
Donald Trump is an American version of right wing opposition politicians of Europe. It's easiest for those with no governmental experience to be certain about what is necessary. Ideas about closing borders, expelling suspicious populations, and imposing controls on schools, religious centers, and youth gangs not only come up against entrenched norms. They also defy implementation, or make its accomplishment of questionable value against the costs in hiring administrative personnel, training them, and controlling their behavior. Doubtful, too, is their capacity to achieve anything like complete closure, as bored guards come up against artful terrorists trained to elude them. 
There are those who advocate establishing a European military force to attack the source of the terror.
Yet Islamic terror is a many-headed monster, with a minimum of inter-group discipline and no established capital or administrative infrastructure to be captured and controlled. The US campaign against the Taliban had such limited and temporary success as to render Afghanistan a poor example of what Europe could aspire to achieve elsewhere in the Middle East,  Central Asia, across North Africa, and down into Nigeria in the West and Somalia in the East, and  wherever else there are large pockets of Muslims intent on attacking the unbelievers.
For those thinking of a Crusade, the first targets might be the Muslim neighborhoods of European cities, i.e., places where the police are loath to enter.
Still unresolved are the problems of what to do with the millions of refugees flowing from chaotic or failed states in the Middle East and Africa. 
Europe's temporary solution--coming when an initial response of humanitarian welcome soured after a short period of time--is paying Turkey to take care of those from Syria, Iraq, and Afghanistan. There is also a plan, as yet unimplemented, of sending many of those who reached Greece and then other European countries back to Turkey. It may not be long before the misery, hopelessness, and violence of refugee camps demands something more from the worthies of the world. 
The European Union is as close to the latest terrorist attack as is physically possible. Television reports of the attack on the Brussels metro station have been set against the nearby headquarters building of EU administration. The Union has succeeded in imposing various agreed-upon regulatory measures through much of its mandate, but its limits appear in the waffling of individual states with respect to the entry of Muslim refugees, as well as Britain and some other countries staying out of the Euro zone. 
The United Nations is far below the EU's league in its capacity to decide and implement. It's a great place for representatives of the weak to speak as if they are powerful enough to decide about important issues. The internal politics of the UN are well known for operating at the level of a grade school's student government. The latest insult decided by Israel, and not likely to accomplish anything more than countless earlier insults, is for the circus called the United Nations Human Rights Council to nominate an anti-Israel activist for the task of investigating Israel's relations with Palestinians.
Wikipedia provides what it designates as an incomplete, but long list of terrorist incidents occurring in the European Union from September, 1958 to this week.
It's been hard to find a serious commentator who expects a major change in policy as a result of the recent incident. Expressions of revulsion and mourning have come from near and far. Israel's Prime Minister has tried to clarify the linkage between the attack on Brussels and efforts against Israel. We've heard from Belgians who say that they do not want to adopt the extreme measures of Israel.
Iran, Turkey, and Israel may agree in condemning terror, but not in defining what are the sources of terror and which places should be attacked. Belgium's initial response was to close its airport and other means of public transportation. Skeptics perceived this as a measure to forestall other attacks primed to occur, rather than to allow the implementation of anything new likely to prevent future attacks.
Time will tell, but optimism is in short supply.
Comments welcome
Ira Sharkansky (Emeritus)
Department of Political Science
Hebrew University of Jerusalem