I completely agree that the government should not choose winners and losers! Consequently, we must END THE FIRST CLASS MAIL USPS MONOPOLY and allow any company to service this niche. Also, no more money from the taxpayers for the USPS!
Once you come to an understanding of which laws create what privileges then you can figure it out from there.
Turns out you aren't really up against the Postal Service ~ rather you are up against the entire United States banking system ~ and as you've just seen they can tap the Treasury for 2 trillion dollars and nobody bats an eye. USPS is small potatoes in that traffic.
Going beyond that, USPS is simply the federal government agency set up to allow YOU and I access to the letter mail business. Without USPS you have no access since it's otherwise a monopoly of the bankers who have no interest whatsoever in your pitiful small contribution to the stream of letters.
BTW, the federales have this right through the 'post offices and post roads" clause in the Constitution so you'll need to change that too.
Lotsa' luck