When an El Niño is declared in the pacific basin Southern Hemisphere . That is the declaration for both east and west of the basin. But the weather effects are different on either side of the basin.
This is due to the bi polar nature of warm/ cold anomalies across the equatorial region
This pattern swings back and forth somewhat erraticically and is called a quasi cycle.
Here is some reading on the weather variation on sth America.

https://www.answers.com/...ino_affect_South_America