Europeans may not be quite so unarmed. According to a 2007 survey cited by wiki, gun ownership in Germany, France, Netherlands, Norway and Sweden is just over 30 guns per 100 residents. That compares to 45 guns/100 residents in Switzerland and 112/100 for the US.
A word about the survey. It looks like the source is one of the usual suspects, so the figures are probably way low. However, I think the ratios might be more reliable. Looked at that way, the northern Europeans have over 2/3 of the arms that the Swiss have.
https://en.wikipedia.org/wiki/Number_of_guns_per_capita_by_country
Those numbers are as accurate as election polls. There are tons of unregistered guns all over the world and who knows how many are lost in rivers.