You're mentioning countries that are racially and culturally homogenous, though, and adhere to 'high values'. In Norway, culture dictates that murder is always wrong. In Japan, culture dictates that to kill is a crime against honour, which is why Japan forces murderers into a psychologically destructive prison regime and executes them at random times. If you want another example of a country where not the lack of firearms but racial and cultural homogeneity lead to low homicide rates, that's Iceland. There are around 90,000 privately-owned firearms for 325,000 people in Iceland, and yet their homicide rates are among the world's lowest (save for some microstates and Japan).

In the United States, you'll find that it's not that easy. It's not rednecks with legal guns doing most of the killing, so taking their guns away would be fairly useless. Even if you take all civilian firearms, you'll find that homicide rates won't change much, as they haven't changed that much in places where firearms have been banned already. The United States is culturally and racially diverse, and you'll see that different cultures have different approaches to murder. African-Americans, for example, tend to be a lot more casual about violence in general and about murder, something which is exacerbated by the gangster culture that is omnipresent in their communities. As a result, African-Americans are the perpetrators in a majority of all homicides in the United States despite accounting for much less than one-fifth of the total population.

Basically, the only way to drastically lower homicide rates would be to export the current American population and import Iceland's, or Japan's, or Norway's. It's the attitude that kills, not the gun.

EDIT: Oh, and if you want the exact opposite of Iceland, try Kenya. That country has some very tough gun laws, and also one of the world's highest homicide rates.