Have you ever played with blocks where one block was holding up another block, and if you took that block out, the whole thing would fall down? That's kind of like what complex interdependence is.
It means that different countries and people are all connected to each other in lots of different ways. They rely on each other for things like food, clothes, money, and even ideas.
For example, your shirt might have been made in a different country, and the cotton for it might have been grown in yet another country. That means that people from different countries had to work together to make your shirt.
And if one of those people or countries stopped doing their part, it could mess things up for everyone else. That's why countries and people often have to work together to solve problems and make sure they can all keep getting what they need.
So, complex interdependence is like a big web of connections between different countries and people, and it's important for everyone to work together to keep that web strong.