Well, I have no experience with Portugal, so I will concede that, regarding Portugal, you may very well be correct, and the speculative investment housing bubble has some underlying cause other than North American-style Euclidean low-density zoning.

I believe that my argument does apply in North America (as well as other English-speaking countries that have copied American city planning ideas, such as Australia, New Zealand, and to a slightly lesser extent, the UK), though.