> The simple fact is, if you drink untreated water, you’re taking on a non-negligible amount of risk.

I wonder how much the propensity for American backpackers to filter water comes from the actual risk faced while drinking water in US rivers, and how much come from the crazy risk aversion in the US society nowadays. In Norway or Sweden, backpackers often don't carry water bottles and drink directly from the river with a cup. In France, I've never met someone filtering water.

The same way, parents can't let their children play outside or go to school alone in the US, while it's often the norm in many parts of Europe. There is indeed a “non-negligible” risk, but individuals put the threshold higher.