USPS is not yet allowed to change postage rates
The U.S. Postal Service cannot currently change postage rates because its Board of Governors has been empty since late 2016, although President Trump's first three appointees will have Senate confirmation hearings next week.
Why it matters: Trump has criticized USPS for losing money, and yesterday formed a task force to explore possible reforms — two things that might not have been needed were governors in place.
Yes, but: Trump's issues with Amazon won't be solved regardless of what happens with the appointees. Individual mailers like Amazon agree with to negotiated service agreements that are approved by a separate body called the Postal Regulatory Commission, whose bipartisan members also are appointed by the White House. Currently, three of the PRC commissioners (including the Republican chair) were appointed by President Obama, and one by President Bush.