The NFL has had male components to cheerleader teams for some time, though when is debatable. The first NFL team to have Cheerleaders was the Baltimore Colts, which was a component of the mostly male Baltimore Colts Marching Band in 1954, though the first permanant NFL co-ed cheer team would be the Baltimore Ravens cheer team in 1998. Co-ed cheer teams in the United States are not unusual and most high schools and all college cheer teams in the U.S. are co-ed, despite the sport having a 95-97% female population as a whole. Men are often used on the team as the base for stunting (the pyramids) and will lift the flier (the people on top of the formation (typically a woman) up and act as support while the base will support her and the spotters (also typically men) will act as a human safety net for the flier.
Recent compittions will actually make some more technically difficult stunting techniques illegal for an all female team but legal for a co-ed team, as on average, men tend to be stronger than women and thus more than capable of holding the weight of the fliers, who are often the smallest members of the team.
And most male cheerleaders are not the small dudes. The Wikipedia entry for cheerleading features a picture of the West Point (Army military academy) stunting for Donald Rumsfeld and the men all look like they would have had a decent go at playing on the football team (all U.S. military academies require students to participate in an extra-curricular sport).
As discussed in another answer, there is some legal leeway for the entertainment industry to discriminate based on entertainment needs. For a non-sports example, a director making a film based on Shakespeare's Othello, may pass on over qualified Shakespearian actor Patrick Stewart for the titular role based solely on Mr. Stewart's skin color, because the titular role is a man of African decent (incidentally, Stewart did apply to play another role in a film production of Othello, but the director decided to cast him as Othello, with the rest of the cast being entirely of African decent... the play is about Othello being of a different ethnicity than the rest of the characters, so it worked here.).