So, you know how when you want something really cool, like a toy, you need money to buy it? Same thing goes for countries too! They need money to buy things they want, like weapons and food for their soldiers.
Well, a long time ago, the United States of America wanted to become their own country and not be ruled by England anymore. This made England really mad, and they started a big fight with America called the Revolutionary War.
But, fighting in a war can be really expensive! The United States had to spend a lot of money on things like weapons for their soldiers, food to feed them, and clothes to keep them warm. They also needed to pay people to work on building forts and boats.
To get all this money, they did a few things. They asked people to donate what they could, but that wasn't enough. So, they borrowed money from other countries and even printed their own money, which is called "currency".
But borrowing money means you have to pay back even more money later, and printing too much currency can make it worth less. So, after the war, the United States was left with a lot of debt, which is like when you owe someone money.
The debt they had to pay back was really big and lasted for a long time, but eventually they were able to pay it off by making wise financial decisions and growing their economy.