Impoving wines from outside Europe

Well it is a combination of the factors you have stated like better flow of knowledge and technology from Europe, more local experience. But there are two more things  :

the vineyards are getting richer and the can afford better machinery , fertilizers , pesticides and personal.

The vineyards are getting older , a vine produce it's best grapes at the age of forty or so.

Along with what bergerui wrote there is the factor that importers are starting to import them. Lots of regions make great wine(Hungary and the Chezch Republic two name two) but when do you ever see those wines in your wine shop? 

Here in Spain the wine was good before but the style was not what people in other parts of the world were used to. "GOOD" is a matter of opinion, and when some Spanish producers saw what others considered "good" they changed their methods of wine making.