ASP.NET MVC5: live loaded partial view doesn't load dynamic Javascript reference

My goal is to refresh a partial View containing an interactive world map. I have a Controller action

public JavaScriptResult DynMap(int id, List<int> relevantCountries = null){}

which returns the map data as JavaScriptResult.

I call this Javascript in my Partial View "MapSite" with

<script src="/JS/DynMap/@ViewBag.GameRoomID"></script>

The Partial View "MapSite"

public ActionResult MapSite(int id)
{
   ViewBag.GameRoomID = id;
   return PartialView("MapSite");
}

is rendered into my main page like this:

<td id="map">
    @{Html.RenderAction("MapSite", "JS");}
</td>

That works perfectly fine! But if I want to render MapSite again at runtime (with new values) like this: $('#map').load('/JS/MapSite/4')(4 is static for testing), the Partial View comes without the DynMap Javascript.

Is this a bug? Isn't it possible to load external Javascript this way "live"? It even hits the breakpoint inside the Controller DynMap method, but the map is empty, because the DynMap values are missing.