Funny enough, CECOT only exists because of this. MS-13 started in the United States, and only spread to El Salvador because of deportations, making El Salvador completely unlivable.
You cannot discard the role of US Immigration & Deportation policy in the rise of MS13 gang.
Please read some books on the matter if you disagree. My recommendation is "Unforgetting: A Memoir of Family, Migration, Gangs, and Revolution in the Americas"