What would Dr. Doom do? He's the ruler of his own nation. The only reason he's ever seen as a super villain is because of his homicidal obsession with Reed Richards. And there's no real way he'd be able to take advantage of Civil War to go after Richards. Especially since, now that Reed's a deputized government operative, atacking him would not only put Doom's diplomatic immunity in jepordy but very likely spark a war between the United States and Latveria, which Latveria would almost assuredly lose, or at least be much worse for the wear than the U.S.