The headline and subheadline laid out the problem; the article expands on it.

Naturalized but radicalized: Recent terror attacks expose glaring problems with citizenship vetting
After four attacks on the U.S. with one common thread—immigration—the time may have come to make transformative changes to the system that decides who comes in.

That’s a mostly accurate description, but only that; Congresswoman Harriet Hageman (R, WY) identified the other critical dimension of the problem.

Throughout history, we have expected people who immigrated here to become assimilated to the American culture. And I think over the last 30 years or so, there’s been this idea that we no longer need to do that, and this is an example of the consequences of those kinds of bad policies[.]

Our vetting does nothing to assess a potential immigrant’s interest in or willingness to assimilate into American culture, a culture that prizes individual initiative, individual responsibility, and acceptance of, or at least willingness to, live under American values of free speech and religion, keeping and bearing arms, and the rest as illustrated in our Bill of Rights.

Once in the US—legally, mind you—and on what amounts to probation, remaining here on a green card or while on the green card working toward citizenship, potential immigrants are not pushed to learn American English (or even British English) beyond taking a few simplified English as a Second Language courses, nor are they required to learn about American culture and values beyond what it takes to pass a dumb-downed citizenship test.

English needs to be specified as our official language, and government officials at all levels of our hierarchy need to interact with citizens and immigrants in English. Beyond that, their children need to be taught in American English in school, not in their native language, and that schooling needs to include more American history and civics (as it must for the children of us citizens, come to that).

With no incentive to assimilate anywhere along the way, potential immigrants, staying separate from us, gain a sense of isolation even in their enclaves. Of course they’re easily radicalized.