I am not trying to paint a rosy picture or deny that poverty exists in the US but I found that an average of 3.6 percent of Americans suffered from hunger in 2004/02 according to the USDA:

http://www.ers.usda.gov/publications/err11/err11appD.pdf page 2 table D1

Prevalence rates of food insecurity and food insecurity with hunger
by State, 1996-98 (average), 1999-2001 (average), and 2002-04 (average)

This is less than 1 in 27.7 adults and kids, not 1 in 5 but it is still to high.