I guess we aren't as innovative as people like you would have us believe, then. I am sure we could get along without them. People might have to learn to cut their own grass. Or, invent and build something that might do it for them. I do not ascribe to the notion the we would be helpless without 11 million criminals in our midst.
In general Growth, Innovation, Productivity will all slow or reverse.
I guess you didn't read Krikorian's dissertation on this subject.
"But it's the second part of the response to a tighter labor market that people just don't get. By holding down natural wage growth in labor-intensive industries, immigration serves as a subsidy for low-wage, low-productivity ways of doing business, retarding technological progress and productivity growth." Found here.
I am sure you won't agree with it but that's just because you seem to have a personal stake in this issue.
The simple truth is that these people are not as vital as you would have us believe. In fact, the exact opposite is true. They are a drain on us economically; they are destructive to the American culture; and they are not loyal to America.