Apparently ending the de minimus exemption is closing the grey market for e.g. sunscreen; places that used to sell Japanese sunscreens on American shelves no longer are.
There's a frustratingly long list of goods that the US decided to put requirements on in previous generations, and then stopped maintaining. Sunscreen is one; other countries have invented sunscreens that feel better on your skin than the old styles, but aren't yet approved in the US. Motorcycle helmets are another. You may have seen the MIPS system - the yellow slipliner that's become popular in bicycle helmets. Scientists have realized that rotational impact leads to concussions and similar brain damage, but prior helmets only protected against naive impacts. Europe now requires helmets to protect against rotational damage. The US requires that manufacturers self-assert that they meet a very old standard that ignores rotational impact. They do not recognize Europe's new standard.
Closing these de minimus exemptions is making it harder for discerning consumers to buy higher quality goods than are currently available in the US right now. Protectionists are going to see this as a win.
More background on helmet standards: