If we pass laws to allow anyone to cross, then it will all be "legal." You have to be more specific about what you oppose.
Many claim that the illegal immigrants drive down wages here...and that they are taking jobs from Americans. Would not the unaborted have done that? Or do you disagree with the premise?
I'm just asking, not disagreeing.
Your premise has not occurred yet.
I am against people coming here illegally. It is not theoretical--they are net social service users, and causing a drain on our society. The justice system, the medical system,the education sysytem, and the social services systems are being strained by an invasion of people who should not be here, but in their home countries.
I think that is specific enough.
We cannot know what America would be like with the missing 60 million people, It could have developed in many different scenarios.
However we know what the reality is today.