Long Island, where prosecutors say two girls were beaten to death by MS-13 members in 2016, is one of the many places where the gang has expanded. The police have been fighting the gang there since 2007, but MS-13 continues to murder and grow more powerful because the authorities have failed to attack the organization at its roots.

The people accused of killing those girls were not hardened murderers with tattoos, members of a “cartel,” as Mr. Trump described the gang in 2017. They were teenagers. They were also part of the gang’s hard-core American ground forces: young immigrants, either with or without papers, lost and lonely in a new and violent world, where they have responded to the first institution that has lent them a hand — MS-13, not the United States government.

To say that the gangs “win over” these young people is misleading, because it implies that the American government is doing something to compete with them, which it is not. The United States is not fighting for these boys.

Americans keep talking about deportation but focus comparatively little on how budget cuts in education serve to feed gang recruiting activity, as Howard Koenig, the superintendent of public schools in Central Islip on Long Island, recently pointed out.

Americans also keep talking about the wall President Trump wants to build, but few people have acknowledged that “the government’s total failure to establish an efficient process and meaningful oversight of the placement” of unaccompanied minors has led to the MS-13 crisis, as Senator Charles Grassley, Republican of Iowa, said last June. Many of these children come from dysfunctional families, with parents who barely have time or money to take care of them; the government essentially releases them to the streets. Of the more than 240,000 unaccompanied minors detained at the border since 2012, only 56 were suspected of having connections to MS-13 when they arrived. If they made those connections after entering the United States, the United States is to blame.

Mr. Trump will continue to use his favorite word for MS-13 gang members: “animals.” And few people will focus on the fact that at high schools like Uniondale, home to two of Long Island’s MS-13 clicas, there are only three social workers for over 2,000 students. One of those social workers, Sergio Argueta, told me that many of these students are recent arrivals still lost in their new surroundings. He works to help at-risk youth in Long Island through an organization called Strong.