Unpopular opinion, but if you let EVERYONE into your country, aren’t you just co-opting an entire population?

If things are so good in the US, then you just let all asylum seekers in, wouldn’t you just stack in stacks of people? I’m missing how border control is a negative at this point. They aren’t talking about denying people from a humanitarian stance, just go through the proper channels.

What is so crazy about this?