Suggestion: Take some turns to consolidate your empire.
Don't do it yet. You have to prepare. Take South America while you are preparing.
Prepare for the consolidation by building Freights and establishing trade routes. (You don't have to do it exclusively) An airport in South America and another one in Supi would make trade routes to Supi easy. It would also allow sending Freigh units from South America to a Transport in Supi.
Trade route to another island = 2x income. Trade route to a far away city = high income. Trade route to a foreign city (2x) on another island (2x) = 4x income. So trade routes from South America to the foreign cities next to Supi should be lucrative (unless they are small).
Another part of the preparation is to make sure your cities can produce more food than they consume. (See Harbor, Supermarket, etc) 1 surplus per turn is enough.
The final preparation is to move your units inside your borders. This avoids unhappiness.
Start the consolidation by turning you Luxury rate up to 40%. No units (except Freight, their transports and spies) should be outside of your borders. This should make your people extremely happy. Happy enough to celebrate. Make sure that your cities produce more food than they consume. Focus on building Freights (to get more trade routes) and Engineers (to improve the land and clean up the pollution). If a significant number of your cities size 3 or above doesn't grow within 3 turns you should increase the luxury rate, make sure that they have trade routes/happiness buildings or check again that they have enough food.
End the consolidation once your cities have reached their current population limit (Aqueduct, Sewer system) or are are large enough to have the production and income and science you wish.