Homer wrote: How would we determine who was imperiled?
We take their testimony.
Will some persons say they are imperiled, when they are not? Possibly. But shall we risk turning people away to be butchered, because we're afraid of receiving somebody who doesn't have such dire need?
The US has the material capacity to absorb every human resident of the Northern Triangle, regardless of peril. And most folks are not eager to leave their homes and communities and venture out to a strange land without compelling reason. By and large, we would be receiving people who are seriously imperiled, and people who are seeking better opportunities in life. Folks of the first sort, we have a responsibility to help. Folks of the second sort, generally turn out to be an advantage to our society - with some exceptions, but (data indicates) no more so than our native-born population.
Homer wrote: Those who imperiled them would probably join them. many already have.
Not really. The US is not a fertile environment for those parties. They cannot thrive here, using the playbook they are accustomed to.
Homer wrote: I do believe laws should in general be obeyed.
I agree. Which is why it is important to change laws that are not just. Unjust laws inevitably need to be disobeyed. And the pattern of disobedience undermines the social effectiveness of all laws, including those that are just.
Homer wrote: I do think that without immigrants our agricultural system would collapse. ...
That is important to consider.
But I will point out - your remarks seem to revolve around the interests of people in the US. This reminds me of certain parties in the abortion debate, who speak extensively about the interests of the mother, and rarely or never about the life-or-death issues involving the unborn.
In the abortion debate and in the immigration debate, we must not focus on one class of persons, to the grave neglect of others.