Well, emo is short for emocore, and it seems to be an American thing.

Stylistic origins: hardcore punk, indie rock
Cultural origins: mid 1980s, United States, Northeast Mid Atlantic, New Brunswick, NJ, Washington, DC
Typical instruments: Guitar - Bass - Drums - Synthesizer
Mainstream popularity: various eras from mid-1980s to early 90s; early 90 to mid 90s, late 90s to current
Derivative forms: 21st Century

Emo Subgenres: emocore, hardcore emo, emo violence, screamo, midwestern emo
Fusion genres: post-hardcore
Regional scenes: California - Washington DC - Midwest - New Brunswick, NJ
Other topics: Emo fashion - List of early Emo groups - List of Emo groups - Timeline of alternative rock
http://encyclopedia.thefreedictionary.com/Emo