In all countries where pornography is legal sex on webcam is legal but of course everyone must be an adult over the age of 18 years of age. So yes live sex chat sites where you watch others naked on webcams performing sex acts is legal in all those countries where porn is legal.
So in conclusion the answer is YES sex webcam sites are legal where pornography is not outlawed. Adult chat sites and sex webcam sites are legal in all the the United States and Europe. See which sites are the best adult chat sites. (Link to list of top chats sites)
Here is a map of which countries outlaw pornography. Obviously once again everyone MUST BE OVER THE AGE OF 18!
Bonus: For fun we also included a map of the most popular porn hub searches in all parts of the world.