Is it [still] true U.S. postage rates are among the lowest in the developed world?

[cckerberos]

@Ximenean

That 41p is good for mail up to 100g, though, which is about 4 “ounces”, as they are quaintly called in the US. According to the USPS website, that would cost either 95 cents or $1.39.

So we may be comparing apples and oranges. If what you say is true, the Royal Mail overcharges compared to the US on standard letters, but undercharges on heavier ones.