Badly. Until a few years ago there was a franchise-wide rule that no food could be discounted even if it was close to expiry, so either the staff/owners bought them and ate it themselves, or it went in the dumpster.
Giving expired food to homeless people is not really a thing there either.
South Korea has extremely strict food waste laws and a pretty well developed systems of convenience stores. I wonder how things are handled there.
If that works (badly) in Japan, then why can't it work (just as badly) in the US?
What new impediment does the geography bring to the table?
Convenience stores changed a lot around 2010 when they started real time tracking Every Damn Thing. Even in the mid 00s staff ate, took home, or gave away whatever they wanted to from the expired pile.