Based on the greenhouses I could identify on google maps spain's part seems much larger.
Netherlands - https://www.google.com/maps/@52.021357,4.5405597,46292m/data...
Spain - https://www.google.com/maps/@36.7995257,-2.4654344,60237m/da...
Netherlands - https://www.google.com/maps/@52.021357,4.5405597,46292m/data...
Spain - https://www.google.com/maps/@36.7995257,-2.4654344,60237m/da...
https://www.nationalgeographic.com/magazine/2017/09/holland-...
Also, it's not only about size, also efficiency. Scroll down the article and look at the insane yields per square mile for tomatoes, chilies + green peppers, and cucumbers. No other country comes even close.
https://www.freshplaza.com/article/2135083/netherlands-world...
The only good tomatoes from these parts of the world I have tasted were cherry ones. Not sure whether it is cultivar, climate, agricultural practice or terroir. But they taste nothing like real tomatoes.