If anything, the cause of the most recent real estate crash (and subsequent rise) was the overwhelming covariance of real estate trends throughout the country/developed world.
Agreed. Though, I could imagine a RE market correction breaking the correlations - if only through bankrupting the market players forcing that correlation. i.e. I'm in rural America seeing commercials for cash RE buyers from mobile applications. That's got to be indicative of factors correlating markets intimately. I'm also wondering whether this indicates new factors actually creating connections between markets that weren't previously there - or simply hubris.