And it’s all unnecessary. We’re a rich country — and citizens of other rich countries don’t worry about being bankrupted by medical expenses
Krugman describes that there is nothing to worry about and that citizens of such a high class country would not get bankrupt from only these conditions. The author uses a different tone for this to describe their concerns. The tone shifts from worrisome to careless almost casual about the entire situation to comfort his audience and not end on a harsh tone which would create tension in the reader.