You are missing that Spain's economy is not growing like the USA's.
Spanish wages grew only 2.7%/yr L10Y [1], and its nominal GDP/capita looks completely flat [2].
This explains why the city is affordable for international tourists but not locals. Regardless, a high "tourist tax" would probably be better for their economy than an outright ban.
At 2.7% that's 2.7% and .7% growth faster than wages.
Let's look at the bay's wage growth[0]: 11% (or ~1%/yr) from 2010-2020, but they removed CPI-U inflation[1], so it's something higher (annual was ~1-3% in that time period). Which puts the bay area housing at 5%+ higher growth, 2x to 7x worse than Spain.
So, once again - Spain is doing well when it comes to housing prices. Tourism frustrates locals because they think it's increased their housing costs wildly - but in fact it's because their economy is switching to a tourist economy unless they find an industry to grow.
70% is ~5.4% yearly, 40% is 3.4% growth yearly. Seems, fine?
These are incredibly reasonable growth rates. Am I missing something?