@janmarco: RES originated from US specifically Florida and the neighboring states.. They are now widely available due to worldwide pet trade...
Quote from
www.redearslider.com :
The Red Ear Slider geographically originated from the area around the Mississippi River down to the Gulf of Mexico. They will thrive in warmer climates, particularly the Southeast quadrant of the United States. Such an area would be east of and below Colorado to Virginia down to Florida. The pet trade has expanded their range around the world, often at the expense of native terrapins. Therefore, it is not difficult to locate RES in some suitable habitat anywhere in the world.
Hope this answers your query.. Thanks..