See https://news.ycombinator.com/item?id=36777125 for a breakdown of what it would look like with an example portfolio in Valencia. The tax differs by region and is highly progressive. For a 2M portfolio in Valencia it ends up cutting 0.7% off your safe withdrawal rate after exemptions if you split it between a married couple. It makes it harder to retire early, but don't forget about additional US costs like health insurance, vehicle, etc.