Is this the end of the practice of mailing lamps to one another in the USA?
I assume this was always the case? At-least with the USPS
However they seem to be getting more strict with all of HID and fluorescent lamp bans in many of the US states now

Hope this won’t become a thing worldwide 

 They've been saying that for awhile now . I just don't tell them . When they ask "Anything fragile , liquid , glass or containing mercury ?" I just say "Yes , glass. "

I would be curious to know the "threshold" amount from a legal point of view. Most lamps use a quantity of mercury that is, on an absolute scale, tiny. The examples given are mostly of devices using a bunch to a monstrous amount of it.

The event of say a mercury barometer breaking is a catastrophic scenario, from both health and environmental perspectives.

Then you realize someone on YouTube made a video on running a toilet on mercury...