Shipping something from Germany to Argentina cost €3.70 recently; the same thing (a large padded envelope, about 400g) would appear to cost $7-8 if from Chicago to New York. If that's unfair, who's at fault?
EDIT: I ask because the Chicago-NY price is >100% above German international rates. >100% is a big number and German prices are high to begin with. That makes "part of" too fuzzy for my taste.
Meanwhile, the US Postal service is a quasi-government agency that is predictably a mess. On one hand it is supposed to be self-sufficient but on the other hand it is burdened with federal agency restrictions or limitation. And, it distorts the mail market in general by having a government granted monopoly on regular mail.