Fishmanpa - 3 million is around one per cent of the US population, not 0.01%.
That's one in every hundred people, and they will be more represented in certain communities.
Just think of the logistics of trying to deport one in every hundred people from the whole country. It would cripple the economy just trying to do it. It's a typical example of what's called a "thought bubble" that just doesn't stand up.