It doesn't really seem like God and the Sears catalog ought to be linked in someone's mind, but they were for Jenne during her time at Manzanar.
The reason why they were linked is that both of them represented things that could not be gotten there at the camp. Both God and the Sears catalog represented good stuff, stuff that they were not able to easily get while in the camp.
Jeanne even starts sort of confusing the two. She prays for dried apricots, but she fantasizes that they will come in a package from Sears.