1. The goal of the charity was to help its target demographic integrate into U.S. society.

2. The goal of the charity was to help its target demographic integrate into the U.S. society.

======================================================
Do we have to use U.S. society or the U.S. society? Do we need to put 'the' before U.S. society?

You can use it or not, as you wish. I think without ‘the’ is more usual, though.