In democracy 3 the military was not very useful and there was also very little one could do with regards to foreign policy.
This makes no sense considering the importance of foreign affairs in real-world politics.
As I understand it military conflict and diplomacy is not something the game is aiming for which is understandable however I believe there must still be some representation of international relations.
1.War on Terror: Terrorism is still rampant on an international scale. There could be for example a metric which would measure the prevalence of international terrorist organizations which would affect trade and the oil supply
as well as inducing fear among the citizenry and increasing the likelihood of domestic terror attempts(there could be a negative situation(similar to the race riots situation for example) to reflect problems caused by domestic terror)
2. Crises: There could be international crises a nation could be affected by at the start of the game(similar to the problems that countries had at the start in democracy 3 Africa).The U.S.A. could start involved in the Afgan war which would give it various problems or be the leader of nato (or a member of nato) which would provide benefits as long as military spending is high. The US could have the option to increase military spending and tech to win the war or use diplomatic means. Other crises could be for example dealing with ISIS or the Yemeni civil war or disease or wildfire outbreak
3. International organisations: Nations could have interactions with international organisations. For example, a nation could choose whether to be part of the W.H.O. the W.T.O. or N.A.T.O. Or to solicit low-interest loans from the IMF. Participating in an organisation could have various benefits however they would limit your policy options. The IMF would request you proceed with free-market reforms or cut social programs but lower interest rates NATO would increase military spending but also foreign relations and security and WTO would lower your tariffs but increase global trade.
4.Policies: There could also be various policies with regards to foreign affairs.
similar to the drone strike program already in the game. These would be weapons trading and military assistance(very important for nato countries), worldwide SpecOps, foreign counter-terror training, foreign intel sharing, cyberterrorism and cyber operations(quite prevalent these days) or a nuclear program.
Postscript: I would also propose adding two other categories of voter:
interventionists and pacifists who u be in favour of against foreign intervention respectively.
Sorry for being so long-winded