I don't think it's fair to call that wasted, as if the food produced in these wealthy nations could be transferred to the poor nations.
The cause of food shortages in Africa is the fact it's a lot of non fertile land.
The cause of food waste in the United States is that we have a LOT of fertile land and relatively few people.
It would be like blaming my water usage for shortages in the southwest. You have to see that the two systems are disconnected and just because one nation wastes food does not mean other nations are denied it.
Global trade has eased a lot of regional shortages, but geography and environment still matter.
The same goes for famine. We may be able to adapt, but some regions simply will not and even with global increases we may still see regional shortages and famines.
As someone living in the USA, I'm not worried. We will be fine because we have such a large buffer. If you live in an area that doesn't. You have plenty reason to worry, especially if global trade hiccups or you're in a relatively poor nation vulnerable to trade disruption.