I'd say there are a few things he massaged to make his point. For instance, all infrastructure doesn't double, not everyone in the 3rd world is trying to immigrate to the US and the ones who do immigrate legally are from the highest economic class, not the lowest. Political asylum and humanitarian immigrants are very few.
The immigration rules only allow university educated people, those with special skills requested and required in the economy and those with enough cash to start a business and hire people. The lottery for green cards is only (iirc) 50,000 people per year. So, I'd say illegal immigration is far more important of an issue than legal immigration.
Immigration (legal and illegal) is not just an American issue, either. It's happening across the world because there are just too many darn people everywhere.
