Starting February 4, this change won’t affect the delivery of letters and flats from those regions. The USPS hasn’t commented yet on whether this is related to President Trump’s decision to end "de minimis" shipments from China and other places.
Trump's move to stop Section 321 de minimis is part of his plan to impose an extra 10% tariff on China and 25% tariffs on Canada and Mexico, although those tariffs have been paused for a month.
According to a report from a U.S. congressional committee on China in June 2023, nearly half of all packages shipped under "de minimis" come from China.