The group now counts 11 red hats who will cast ballots. Eight were elevated by Pope Benedict XVI.
Catholicism is America's largest religious group, and it's still growing thanks to the wave of immigrants from Latin American countries.
The seeds of this U.S. bloc, if it is to materialize, were sewn at St. John's Seminary in Camarillo, Calif., where Rigali and two other future cardinals, Roger Mahony and William Levada, entered the priesthood together.
Among them, the "Camarillo cardinals" have connections and experiences that could draw support for their agenda from practically ever major conclave constituency.
Mahony, the former archbishop of Los Angeles, is a tech-savvy progressive whom John Paul II iconically dubbed "Hollywood." Levada is a moderate theologian who shocked many by becoming Benedict's first red hat. And Rigali is a quintessential Vatican heavyweight.
And while they are long shots, America also boasts credible candidates for pope this year: Boston Archbishop Sean O'Malley has made many short lists, and New York City Archbishop Timothy Dolan has also drawn some attention.
The unification of the U.S. cardinals comes at a time of great change for the church in America. The old powerhouse archdioceses of the Northeast are increasingly sharing power with those in the Latino-heavy West and South.
It also comes at a moment when the interests of American cardinals seem to be clashing with those in Rome. The U.S. red caps had been holding daily press briefings during the pre-conclave general congregation, but the Vatican instituted a media blackout until after the election. The stated reason was a high-profile leak to an Italian newspaper by a cardinal. But the effect is to control the narrative before the elections begin.
The Americans, for instance, had been emphasizing the importance of selecting a pope committed to a "zero-tolerance" response to sex-abuse cases, as well as one who is able to clean up the Church's chaotic central government.
Whether the American bloc has a say in who succeeds Benedict will depend on whether they can stick together through rounds of voting. That story may not be known until long after the white smoke rises.
On Twitter: @SeanWalshDN