This is silly because you don't have to imagine any scenarios. Good economic models are based on empirical data, not on imagining things, and "immigrants don't increase unemployment or decrease wages" is just about the strongest empirical result there is.
The reason being that someone moving closer to you increases demand for labor more than supply, and immigrants generally have complimentary (slightly different) skills to natives. So the person whose labor the immigrant most competes with is another immigrant.
As for remittances/brain drain, there are certainly theoretical issues but it seems to be okay in the end because it boosts investment in the originating country.
And if you subscribe to MMT you should love immigrants because they're free "unemployed" people you didn't have to spend money raising so you have greater runway to print more money without inflation.
And if they are illegal immigrants, even better, they will work hard for a very small salary. They even do very little crime because they don't want to be thrown out of the country.
I think in general immigration from say Mexico to US is a loss for Mexico and a win for US.
The reason being that someone moving closer to you increases demand for labor more than supply, and immigrants generally have complimentary (slightly different) skills to natives. So the person whose labor the immigrant most competes with is another immigrant.
https://www.noahpinion.blog/p/why-immigration-doesnt-reduce-...
As for remittances/brain drain, there are certainly theoretical issues but it seems to be okay in the end because it boosts investment in the originating country.
https://www.noahpinion.blog/p/why-skilled-immigration-usuall...