Switzerland's policy of self-sufficient armed neutrality is crucial in two ways. Neutrality has kept Switzerland from ripping itself apart during wars involving France, Germany, and Italy. Every citizen feels responsibility for his country. In Heinlein's world, the vote is restricted to veterans or civilian service volunteers. Similarly, Switzerland's Old Boy Networks rest upon personal relationships between old army buddies.
Military service is compulsory for young men.
Reserve training remains mandatory until late middle age. Finally, the Swiss tend to have reserved, self-disciplined personalities. In other words, they are not much fun. For example, the national hobby is sharp shooting. They tend to make rational rather than emotional decisions.