When I first heard about the attack in Brussels, I wasn’t sure whether I was shocked. I was certain, however, that Europe had fallen.

It is now clear that the attack was carried out by Belgian nationals with ties to the Islamic State, also known as ISIS, in a style similar to the Paris attacks last year. The pro-refugee European left must have breathed a sigh of relief when they learned that the attacks were not directly linked to migrants from the Middle East and North Africa. Nonetheless, the attackers were descendants of immigrants from the region. Why were those European-born, homegrown terrorists influenced more by ISIS than their home countries? Do they consider Europe home at all?

At the very least, the attacks prove that the multiculturalist experiments in Europe have failed miserably. When the older generation of immigrants first arrived, they didn’t manage to integrate into their new home. Instead, they formed their own communities, preserved their old language, culture, values and sometimes even justice system, and passed everything on to the next generations.

It’s not surprising these “homegrown” terrorists don’t consider the land where they were born “home.” Letting people in without helping them adjust to the new identity is irresponsible. Social engineers love the term “multicultural society,” because it sugarcoats their incompetence and the fact that the society has become increasingly segregated. The present influx of refugees and migrants from the Middle East and North Africa may not cause any problems immediately, but how do we know their children (born and brought up in Europe) will be equally benign?

Europe clearly brought in too many immigrants too fast. But why? Economic benefits and compassion.

With their aging populations, major European economies worry they need fresh blood in order to keep their generous pension schemes afloat. A large inflow of low-skill workers, so the thinking goes, could help keep labor costs, and thus prices of most products, low. But unemployment across Europe remains high, with only a few exceptions. Furthermore, official unemployment figures usually don’t include those who are not actively seeking jobs. Why not hire underutilized domestic labor first, in the unlikely event that there is a real labor shortage in Europe? One may also argue that high welfare spending permits Europeans to live relatively comfortably without going to work. If that is true, then the European countries should cut such spending and motivate people to work longer hours. Furthermore, an influx of low-skilled workers will only drive wages down. It’s surprising that more European labor unions haven’t protested open door immigration policies more strongly — perhaps because the left-leaning political parties they typically endorse favor such policies.

The other motivation for unrestricted immigration is compassion. We don’t like to see others suffer. But we mustn’t let compassion override common sense. In the wake of horrific terrorist attacks, compassion should no doubt go to one’s fellow countrymen first. Paris and Brussels have clearly shown that security risks outweigh the pleasant feeling of “doing good deeds.” If we truly care about refugees and migrants, we should address the root causes of their suffering. If their homelands are underdeveloped, we should promote free trade, which benefits everyone. If their homelands have been torn apart by war, we need to help people achieve peace. Importing troubled people doesn’t make their problems go away; it just brings in more unnecessary troubles.

What about ISIS? Some seem to believe that the West has been tough on the organization. But they haven’t been Putin-tough. Russia received criticism for its callous attitude towards collateral damage and its willingness to target groups other than ISIS. But the Russians achieved their strategic goals, namely weakening ISIS, stabilizing Assad regime and strengthening Russian presence in the region. The strategic goal of the West hasn’t been clear since the beginning. It appeared that Western leaders wanted to remove Assad, install a friendly “moderate” regime, avoid a humanitarian crisis and possibly more. These goals, by nature, contradict each other. Assad had a monopoly on force, so the best way to avoid more suffering would have been to let him win the civil war as quickly as possible. The “moderate” rebels were only “moderate” because they didn’t have the weapons and money to be more violent (all sides in the conflict, after all, were very brutal to their captives). The West’s incoherent military strategy allowed ISIS to advance all over the place, inevitably creating huge waves of refugees and migrants.

Europe has fallen. Its leaders are incompetent on both domestic and foreign fronts. And Europe is not alone. The US is facing similar challenges: mass (illegal) immigration from its Southern neighbors and a growing number of homegrown terrorists brainwashed by ISIS and the like. Fortunately, it’s an election year. Let’s hope American voters make their votes count.

Shaoyan Liang is a postdoctoral associate at the Yale School of Medicine. Contact him at shaoyan.liang@yale.edu .