About 500, oo0 children in the United States have cerebral palsy. It is the most common childhood physical disability. About 3 children out of every 1000 will be born with cerebral palsy, although the rates fluctuate a bit year to year.
In Canada, the rate is lower than the US. Between 2004 and 2008 there were 1.92 diagnoses per every 1000 births. Interestingly, a Canadian study that was published in 2014 in the online journal, PLos One, showed that recent immigrants to Ontario had a 23% lower risk than non-immigrants of having a child with cerebral palsy. Immigrants who had lived in Ontario longer had a similar risk to the rest of the Canadian population.
The data for South America has not been consistently collected throughout the different countries. Going on small pockets of data that have been extrapolated, South America has a similar rate to that of Canada and the US- around 2 or 3 children per 1,000.