I'm a flaming liberal, but I'm going to break with many on the left here: I'm okay with limiting immigration.
Unlike Trump and the righties, I'm _not_ okay with limiting it based on someone's country of origin, religion, color of their skin, etc. I'm okay with limiting it based on whether or not they provide some skill that our economy needs.
I would like our country to be more like Canada or a European country in terms of healthcare, maternity and paternity leave, public transportation spending, education, social safety net,etc.
Because of its universal Healthcare and generous social benefits, Canada has a pretty strict immigration system. They have some quotas for refugees etc, but it's generally a points based system. You get points for being younger, points for being skilled/educated, points for speaking English and French. Basically, they want people that are going to contribute the most before becoming a drain on the healthcare system.
We need a certain number of "unskilled" workers, but younger is better because they'll pay into social security and medicare longer. We need more engineers, scientists, doctors, nurses. But from an environmental point of view, I wish we could get to an economy that functions well with zero or slightly negative population growth.