There has been a study done on Dollarization of Canada with the US dollar
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cts=1330747096727&ved=0CEEQFjAD&url=http%3A%2F%2Fwww.bankofcanada.ca%2Fwp-content%2Fuploads%2F2010%2F01%2Ftr90.pdf&ei=yJZRT46jG-vaiQLUw-W0Bg&usg=AFQjCNGr8LknhwlBE2VBYWyVmlN9Wrf8gg&sig2=pYPuqTlSAWgoI11TMYaD-Q.
From
http://en.wikipedia.org/wiki/Dollarization#Countries_using_the_U.S._dollar_exclusivelyAlso the US dollar is used in --
Countries using the U.S. dollar exclusively
British Virgin Islands
Caribbean Netherlands (from 1 January 2011)
East Timor (uses its own coins)
Ecuador (uses its own coins in addition to U.S. coins; Ecuador adopted the U.S. dollar as its legal tender in 2000. [43]
El Salvador
Marshall Islands
Federated States of Micronesia (Micronesia used the U.S. dollar since 1944 [44])
Palau (Palau adopted the U.S. dollar since 1944 [45])
Panama (uses its own coins in addition to U.S. coins. This country has adopted the U.S. dollar as legal tender since 1904). [46]
Puerto Rico
Turks and Caicos Islands
Countries using the U.S. dollar alongside other currencies
Bahamas
Nicaragua
Cambodia (uses Cambodian Riel for many official transactions but most businesses deal exclusively in dollars)
Lebanon (along with the Lebanese pound)
Liberia (was fully dollarized until 1982 the year the National Bank of Liberia started to issue five dollar coins [47] ; U.S. dollar still in common usage alongside Liberian dollar)
Zimbabwe
Haiti uses the U.S Dollar alongside its domestic currency called "Gourde"