And in Russia, it is. That's why they call it "карусель".

In the United States, it hasn't been. The article you link to doesn't even mention the United States. To do it on a large scale requires cooperation from the people running the election, and the US isn't (yet) that corrupt.

The US system isn't completely robust against it, and perhaps some day it will be a problem. But right now there is no evidence that it is a problem, and all of the attempts to "fix" it are clearly aimed at preventing some people from voting.