It's pretty simple logic which is why it's like a foreign language to the progressive left.
If [insert illegal here] was not in the U.S., the aforementioned illegal would not be able to murder one of our citizens. Plus, we would not have to shoulder the burden of a trial and incarceration. You want that high speed train? You might be able to have it if you had a lick of common sense. Instead, your bleeding heart is intent on the importation of warm bodies in hopes of getting their votes.
The jig, it's up.
"Simple" being the operative word. Simple is why it sells so well to feeble-minded Trump fans. It has the ring of truthiness that makes it oh so tasty to people driven by feelings instead of facts.
Consider, for example, a woman murdered by her white husband. According to your "simple logic", if white males were not in the U.S., those aforementioned white males would not be able to murder our citizens. The jig, it's up.
Automobiles kill tens of thousands of American citizens each year. According to your "simple logic", if automobiles were not in the U.S., those Americans would still be alive. Just say no to cars! The jig, it's up?
Indeed, you can apply your "simple logic" to pretty much anyone or anything: police, priests, doctors, bathtubs. The list is endless.
But wait, you object. Those people and things have other, valuable purposes. They are net positives, doing more good than harm. Yes, exactly. And if you'd pull your head out of the bubble of right-wing propaganda, you'd learn the same is true of immigrants, even those here illegally. In fact, the per capita crime rate by immigrants, including illegal immigrants, is lower that that of native-born Americans. Remember that the next time you try to use simple logic to fix complex problems.