Maybe it's because in the USA we laugh at things like Borat and Seth Rogan, both of whom are flippin' hilarious, btw.
How to Be was different. It's almost as though Rob understands how to present himself the way Americans find interesting, unlike Hugh Grant, who is so typical British- I just don't get him.
I won't spoil the movie, but my favorite two scenes were the break-up scene and the mirror scene at the end. Rob is amazingly talented. Srsly.