Do you mean the fourth largest? #1 is the USA, #2 is Canada, #3 is Brazil, and #4 is Mexico in The Americas.
No, I mean what I said before. 1. US. 2. Brazil. 3. Mexico. 4. Canada. I use GDP by PPP - purchasing power parity, which adjusts for the cost of living in each nation. It is unfair to simply use nominal GDP.