For years, Brits dreamed of owning homes on the Costa del Sol in Spain. And for years, the Spanish government built those homes, sold those plots and supported the possibility by loosening foreign homeownership restrictions.

Then the global economy collapsed.

Today, those vacant houses will likely slide into the sea before a buyer can be found, foreign or not. If there is one thing the European crisis is teaching us, it is that a heated focus on home construction can mask vulnerabilities in the larger economy.

Spain is proving to be a case study in the challenges of implementing austerity measures. With the debt crisis looming stateside, America's politicians should take note.

A report from UBS shows the shocking chart (expand by clicking) where unemployment levels in the under-25 age group were quite bad — even when times were good.

Europe versus US unemployment

The 'under-25' classification works for socialist countries, more or less, as a barometer of social unrest. It is a watchtower for those most likely to resist large-scale changes in the form of rioting.

"As the costs of reform and austerity build up in terms of higher unemployment and lower incomes, the population can quickly lose its appetite for change," write the UBS Global Asset Management fixed-income economist authors.

"Spain never really addressed its excessive labor market rigidities because the impact was disguised by a massive construction boom," the report concludes.

But what's more important is that Spain's issues will likely continue to drag on the eurozone regardless of the Greek outcome.

It's proof that one solution does not necessarily help move on to another.

An inability of the United States to reach its own debt accord will likely create pockets of economic concern. These vulnerabilities may come from, as we've seen with Spain, unanticipated sources.