In the twelfth chapter of the First Book of Kings, God responds to the sins of Solomon and his son Rehoboam by dividing the tribes of Israel between Rehoboam (who is allowed to keep Judah only because of the righteousness of his grandfather David) and Jeroboam. At this point, God has made a covenant between both of these families; on the one hand there is the pact with David who "had not failed to keep any of the Lord's commands all the days of his life-- except in the case of Uriah the Hittite" (1 Kings 15:5) and on the other there is Jeroboam who had been told by God that his line would be just as blessed as that of David. Since we all know David's name and Jeroboam's name is so unknown it's almost unpronounceable, you can probably guess what happened next.
Since the Temple was in Judah and therefore under the control of David's line, Jeroboam feared that the people's faith would lead to, at the very least, a hegemony of Judah over Israel. In response, Jeroboam built two golden calves and intentionally led his people into a pagan parody of Judaism. This fear may appear understandable from a political perspective but it is really quite absurd when we consider the fact that Jeroboam had been promised precisely the level of power he had risen to beforehand by the prophet Ahijah as well as the fact that when Rehoboam tried to take back Israel through military force this same prophet simply told the soldier that the division of the tribes was God's will and they all went home.
I don't know how accurate the movie is, but there comes a point in Charlie Wilson's War when Joanne Herring tells Charlie that the reason she keeps bringing God into the Afghan War is (in the last resort) because they need Him on their side. This is an attitude that Jeroboam would have done well to adopt.
The story that is told from the beginning of the twelfth chapter to the end of the sixteenth chapter is one of both God's incredible grace and the natural results of sin as well as righteousness. Both Rehoboam and Jeroboam lead their people into paganism but what happens afterward is very different. From the very beginning we have been seeing God's grace shown to Rehoboam and his father Solomon in gratitude to David (as the Bible says, "love covers over a multitude of sins") and we see this continue not only in the wrath against Rehoboam that has been held back but also in the blessings that are to be poured out over his grandson. After Rehoboam died, Judah fell into the hands of his son Abijah whom the Bible says "committed all the sins his father had done before him" (1 Kings 15:3) and the legacy of unfaithfulness continued but God still did not destroy the lineage of David. Instead, after Abijah died his son Asa became king of Judah and in this we see God raising up a faithful servant (though the Bible does not explicitly tell us that God had a hand in Asa's faithfulness, are any of us ever faithful without His strengthening us?) in honor of the covenant He had made with David. Asa led Judah out of paganism and back to the worship of God and 1 Kings 15:13 tells us that "Asa's heart was fully committed to the Lord all his life."
Compare this with what happened in Israel. After Jeroboam died his son Nadab became king of Israel. Within two years, he and every member of his family were killed. Starting with Nadab, these chapters record six kings of Israel and it is interesting to note how the Bible tells us when each came to power. Nadab came to power "in the second year of Asa king of Judah" (1 Kings 15:25). Baasha came to power in "the third year of Asa king of Judah" (1 Kings 15:33). Elah came to power "in the twenty-sixth year of Asa king of Judah" (1 Kings 16:8). Zimri came to power "in the twenty-seventh year of Asa king of Judah" (1 Kings 16:15). Omri came to power in the same year since Zimri's reign only lasted for seven days. Ahab came to power "in the thirty-eighth year of Asa king of Judah" (1 Kings 16:29). You should have noticed a trend there.
Ultimately what this all comes down to is the faithfulness of David and Asa. Out of this faithfulness we see blessed reign of Asa which was long and peaceful while his ungodly neighbors killed ascended to and descended from power in rapid succession. This is something that I strongly believe would have happened even if God had done absolutely nothing (as he may well have done) except to maintain a relationship of guidance with Asa no different from that any other faithful Jew would have experienced; Asa's reign was the natural consequence of his love for God and the disasters of the kingdom of Israel were the natural consequences of its sin and unfaithfulness. At the same time there is something else happening here very similar to what Christians experience when they give their life to God. We are certainly not saved by works but our decision to accept Jesus is still an act of love and faithfulness and because of that love God's grace passes over all our failings.
