(I'd argue that one can face expedition-grade challenges in the US and Europe. Try US Southwest during the summer, or Northern Minnesota in February)

Three things I've carried in "expedition" settings: (1) several wide scope antibiotics as suggested by a physician; (2) an EPIRB; (3) a satellite phone (today 2+3 can be reasonably replaced by a SPOT in many circumstances).

I'd say that expedition-grade travel, defined as extended and challenging, requires extensive preparation, unless you are willing to seriously risk injuries or death. By preparation I mean learning about the challenges that you are likely to face, and the appropriate responses (and backup).

In that sense, a world tour isn't an expedition - in most parts of the world, people survive quite well. Even if your equipment breaks down, you only risk mild discomfort.

Regarding world touring, I'd suggest reading Tom Allen (this links to bike design. Peruse his website for several inspiring stories).