Earlier quoted context omitted.
Immigration is a huge issue. It implies tremendous demographic and resource management, logistic, cultural chocks, including educational challenges. Of course nations want to control borders. If you don't, you can't deal with the population flow and all of the above. And you need to deal with the above. Just hoping everything will be ok if you don't think about it is like hoping schools will be ok if we don't think a…
And yet, for a long time in the past century, the U.S. dealt with a massive influx of immigration from all around the world, with all of the complications around culture, resource, and education that you mention. But it seems to me that it is one of the chief sources of the country's strength, no?
Besides, while it is a country strength, it did and still do have a cost. Whether this cost is worth the benefit is something you can only answer if you have metrics to do so, and illegal immigration make it hard to have those metrics, or change your policy to adapt to your new situation.
People always see immigrations as being a moral issue first, but it really is not. It has strong moral implications by nature, but it's first a management issue. Just like eduction, science, etc.