There does not appear to be any earthly way to prevent the Papal Mass in Philadelphia which is scheduled for 4 PM, Sunday, September 27, 2015. However, Our Lady has promised that she will be attentive to our prayers offered through the Rosary. Please pray the Sorrowful Mysteries of the Rosary every day on through September 27th.
Other sites have also suggested a Novena to St. Michael the Archangel which is an excellent idea. However, the Message of Fatima leads us to turn to Our Lady of the Rosary (the title Our Lady herself preferred at Fatima) in this time of crisis. Each five decades of our Rosary ends with the beautiful Prayer to St. Michael, so this way, we do both!
Immaculate Heart of Mary, your children turn to you, beseeching your intercession to halt the outrages, sacrileges and indifference to the most Blessed Sacrament! Crush the head of satan and restore the faith!