I've seen what a typical American mailbox looks like. Sorting out actual mail from the various flyers, "news/offers" pamphlets, catalogs and miscellaneous tree-destroying crap requires dexterity and the patience of Job. I particularly liked the way they'd wrap real mail in the offers mini-newspapers so that you had to work through the whole thing before throwing it away, lest your cable or power bill end up in the recycling bin.
If this appeal bears fruit, I confidently expect US citizens to start leaving mousetraps, poisonous spiders and Claymore mines in their mailboxes. If the USPS wants to address its ballooning deficit, it needs to do something about its pension promises. Alienating its customers is not going to help, whatever it might think.