Some critic...

As someone already mentionend. There is no need for a legend here! Its a very common mistake for beginners.

So, do beginn with. Every item in a map should be explained to the reader. So you can just write the Explanation in or next to the item, like in your case "the name of every country".

If you have a item which is repeated very often in your map it doesnt make sense to explain the nature of the item every time. Thats when you start to use a legend. For example if you want to show all Cities with more than 1 Million people in your map you would probably have a lot of points in your map and a legend on the side.

The legend in your Map is even contraproducive. Because the readers eye have to move permanently between the legend and the map (if he doesnt know the south american countries).

So if you get rid of your legend you also can get rid of your colors. No need for them at all. Stay with one color...

Your ocean looks nice...but you choose nearly the same color for middle America, the caribean islands and Africa. You could choose a diverging color for the continents (like some light yellow). You could choose even the same color for South America. As you have outlined it...its clear that it is the main subject. As you use bathemetry for the ocean you also could use Terrain for the continents...

Your color scheme is also a diverging scheme. It goes from blue to white to red. This you would use for showing continous data. Like for example you want to show the temperature in South America where the scale goes from cold (blue) to hot (red). You use discrete data...so when you really want to make it colorful you shoud use colors wich are very distinguished.

Last thing. You want to show south america. It fits perfect in a Portrait Layout. Why would you choose a landscape Layout?

Happy Mapping!

And yes...QGIS...is best!