The film, which stars Dame Judi Dench and Steve Coogan, tells the true story of Philomena Lee's search for the son she was forced to give up for adoption in 1950s Ireland.
A review in the New York Post said Coogan and director Stephen Frears had found "a true-life tale" that allowed them to "attack Catholics".
It went on: "There's no other purpose to the movie, so if 90 minutes of organised hate brings you joy, go and buy your ticket now."
Excerpts from a letter from Mrs Lee were published in today's New York Times, USA Today and the Los Angeles Times.
She said the film was "something extraordinary and quite real", adding: "Despite some of the troubles that befell me as a young girl, I have always maintained a very strong hold on my faith.
"Philomena is meant to be a testament to good things, not an attack. I have been incredibly fortunate in receiving such a warm response to the movie. Just as I forgave the church for what happened with my son, I forgive you for not taking the time to understand my story."