To put it simply, yes. Americans will run a mile if you're billing in currency other than USD. You're looking ca. 80% drop in conversion rate. Approximation is not an option, it's all about perception.

Whereas the ROTW is pretty much accustomed to being billed in USD online and the impact is far lower.

For me, for my market, AUD+USD are mandatory and optionally GBP/EUR are a strong plus.