Word for the perception that the majority of people thinks about something the same way they do

So for example, supposing that I believed in God then because of my own belief I would assume that most people everywhere necessarily also believe in God. Kind of bias in the thought because of one’s own beliefs.

Solution 1:

From Wikipedia...

In psychology, the false-consensus effect or false-consensus bias, also known as Desolator Syndrome, is an attributional type of cognitive bias whereby people tend to overestimate the extent to which their opinions, beliefs, preferences, values, and habits are normal and typical of those of others (i.e., that others also think the same way that they do).

This cognitive bias tends to lead to the perception of a consensus that does not exist, a "false consensus".