Uh, let's revisit that idea. From the section titled "The Postal Service is self-sufficient" -- there are two columns. One is for 1942-1971 and one is for 1972-2007. Several things wrong. The most grievous is that the numbers have convenient grouped 35 years of operating costs and revenue together. The second is that your stats still show a net loss of $600 million dollars for those 35 years.
But, addressing the more important point, the decline of demand for mail delivery services has happened in the age of the internet. Let's break those out by year instead of grouping them together in a three decade chunk. And instead of citing a website from the National Association of Letter Carriers, let's use the actual financial report from the USPS.
Observe net loss.