In 2008-2011 a 40-60% swing took place in many parts of the US. Arizona, Nevada, Florida all being at the top of the list. The number of foreclosures was devasting to those areas. Vegas, Phoenix etc. were hit extremely hard. Many folks placed keys in the mail box and just walked away from properties -- leading speculators and savvy home buyers to come in at rock bottom and buy their homes on the cheap.
History may not repeat itself but it definitely rhymes.
I don't know about the real estate market for each state you cited but if the market activities were driven mainly by speculation and short term flipping then a 50% dive esp. in a highly leveraged market sounds very plausible but it seems that Vancouver has very sound fundamentals to sustain the higher prices.
Vancouver is actually one of the poorest large cities in Canada. Average income in Vancouver proper in 2009 was $43,911. https://www.biv.com/article/2014/9/trick-or-treating-planner...
All this means that Vancouver is the 2nd most unaffordable housing market in the world (after Hong Kong) http://www.theglobeandmail.com/news/british-columbia/only-ho....
Accordingly a housing is already so inflated that a 10% drop means nothing. Even a 20% drop wouldn't make things affordable.