As well as being a data point raised in an attempt to refute a distribution (which never works), there is a radical ambiguity you are leaning on: "they have lots of guns there" when applied to Switzerland does not mean anything similar to "they have lots of guns there" as applied to the US.

In Switzerland guns are mostly long guns that are heavily regulated and are under very tight storage restrictions. In the US guns are mostly hand guns that are unregulated and under no very tight storage restrictions.

So if you want to make an argument from Switzerland, it would necessarily be of the form: "To reduce gun deaths in the US we should pretty much eliminate handgun ownership and require that all long guns be stored under lock and key in a specified manner, only to taken out on state-permitted occasions for military use."