It is a common misconception that foreign nationals working in the US do not pay taxes. They do. At the same rate as a citizen.
Very true. The real issue is that the wages often don't get "recycled" in the U.S. economy, but are sent overseas.
The Indian and Pakistani tennis team guys we played against last week, aren't spending their paychecks at Home Depot to upgrade their houses, since they live in apartments. For an anecdotal example.