From Apple's Final Cut Studio documentation:
In the U.S., closed captioning for broadcast is mandated by the
Federal Communications Commission (FCC). If you’re delivering tape
masters for broadcast, closed captioning may be an important
consideration. Subtitles are usually provided as a convenience,
although translation to a country’s native language may be required
for film festival or theatrical exhibition and will certainly enhance
your ability to find theatrical or DVD distribution there.
Closed captioning is mandated for Canadian broadcasters as well, by the Canadian Broadcasting Act. Standards for assistive technologies like closed captioning are fragmented the European market, although they're being considered in draft standards for Internet television delivery in Europe.
Final Cut's documentation continues:
Closed captioning is a subtitling system designed to make television
more accessible to the hearing-impaired. Unlike movie subtitles, which
are intended to translate dialogue for people who can hear the rest of
the soundtrack, closed captions need to convey all important sound
effects, music cues, nonverbal expressions, and dialogue that occur as
a program plays.
...
Subtitling is usually done for the purpose of translating either
particular scenes or an entire program. It may be done because the
dialogue is in another language or because the dialogue is simply
unintelligible to the intended audience.
The easiest way to add permanent subtitles (sometimes called open
captioning) to your program is also the most time-consuming: editing
superimposed text generators into your sequence one at a time.
Closed captioning is mandated specifically "to meet the needs of Deaf, deaf, deafened, and hard of hearing people" [Captioning in Canada], and so the specific distinction of closed captioning from subtitling is made in the US and Canada (and apparently Australia).
Since most of the rest of the world has no such mandate, they make no such distinction.
