This seems to be a rather naive interpretation of the events.
Pro Guns or Against Guns?
Neither Democrats are against guns nor Republicans are for guns. The debate between them is not about existence of weapons, but the ease of access and the level of weaponry an "ordinary Joe" should be allowed to possess. Should everyone have a small nuke in their backyard? A tank in their garage? Or a handgun in every lady's purse? These are very different things.
Democrats are advocating for more gun control. More regulation on who can own guns, what guns they can own, and what they can legally do with them and where.
Republicans are advocating for the opposite - less regulations, less restrictions, everyone should get anything they want (when it comes to guns, of course, marijuana or books is a completely different matter - those are deadly and dangerous). Well, unless it's for black people, if Republicans see black people with guns - they're all for gun control.
Military Alliances
Military in general, and military alliances in particular, have nothing to do with the individual gun ownership and the debates about its expansion in the US.
Neither the Democrats nor the Republicans are advocating to reduce the US military or limit its weaponry. In fact, the US laws are such that even when the Congress fails to fund the government - the military always remains funded.
When it comes to military alliances and aid to foreign countries, there's very little difference between the Democrats and (mainstream/moderate) Republicans. Trump muddied the waters a bit with his resurrection of the "America First" nationalist movement since the World War I era, but enough Americans (still) remember (either through family history, or education) how that ended up the last time. So the political support for sending weapons to allies like Ukraine, Israel, Taiwan, South Korea, etc. is still strong and bi-partisan.
Gun Violence
The debate about gun violence in the US is about the criminal use of guns by civilians, not about military use. When it comes to the governmental use of force (either by local law enforcement authorities or the Federal armed forces), politicians are very rarely advocating against it. Even at the height of the BLM protests very few politicians would voice any concerns about the police brutality and militarization of the domestic law enforcement, and those I did hear voicing it were mostly on the local level.