As the U.S. population speeds toward 300 million, the growth is producing headaches for Americans fed up with traffic congestion, sprawl and dwindling natural resources.CNN.com - U.S. about to have 300 million Americans - Jul 5, 2006
But of course, it's not 300 Million Americans, it's 300 Million residents of America, of whom 30 to 50 million are foreigners.
In March 2003, the civilian noninstitutionalized population in the United States included 33.5 million foreign born, representing 11.7 percent of the U.S. population. The Foreign-Born Population in the United States: 2003 [PDF]
The figure might actually be something like 260 million Americans, and 40 million guests, some of whom are uninvited.