We're not 100% sure what Dr. Song is a doctor of, but he's certainly got the propaganda patter down. In fact, when he takes the North Korean contingent to Texas to negotiate with the Senator, he's able to best Tommy in a battle of political wits:
Tommy said, "Tell me you at least know that the South won the war. Please know that much."
"But you're wrong, my dear Thomas," Dr. Song said. "I believe it was the Confederacy that lost the war. It was the North that prevailed." (129)
Dr. Song's adherence to party-line politics is his entire identity. There's really nothing to him besides that. Comrade Buc attempts to give him some depth by telling Jun Do a little of his story: "That guy's a survivor. During the war, he got an American tank crew to adopt him... That's what he could do when he was only seven" (163).
But Dr. Song is no longer seven, and his biggest problem is not the Americans. He knows that his failure in Texas signals a change in the life he'd been enjoying so much. Despite this war orphan's triumph over a system rigged to destroy him, he knows he's reached the end of his tether, and he tells Jun Do this before they leave for home:
"I have seen the white nights in Moscow and toured the Forbidden City. I have lectured at Kim Il Sung University. I have raced a jet ski with the Dear Leader in a cold mountain lake, and I have witnessed ten thousand women tumble in unison at the Arirang Festival. Now I have tasted Texas barbecue." (157)
Jun Do is right to get the willies at Dr. Song's speech: the dude's deep in nostalgia mode. The sense of weariness he feels at the end of his mission is a growing awareness that he's outlasted everyone—and that it can't go on much longer. And, in fact, Dr. Song is no more by the time the Senator and Tommy return his visit in North Korea.