https://www.reuters.com/article/us-un-postal-idUSKBN1W91JX

This president* is amazing.

[Peter] Navarro said Washington could quit without problems.

“We have prepared for a seamless transition. There will be absolutely no disruption in military mail, election mail, or holiday mail,” he said.

Another article (https://www.dw.com/en/pexit-us-prepares-to-pull-out-of-universal-postal-union/a-50569818):

It is not, however, the first international body to draw the ire of the current US administration. Donald Trump has already withdrawn the US from the UN Educational, Scientific and Cultural Organization (UNESCO) and the UN Human Rights Council. He has also threatened to withdraw the US from the World Trade Organization (WTO).

The US initially announced its intention to leave the UPU within one year’s time on October 17, 2018.