What would happen if everyone on Earth were sent to prison?

They'd have to change the name from "Earth" to "Detroit?"

then we'd be in big trouble

Then everyone else (those remaining) will be sent to space station or Moon. Sounds good, it might be true in future.

In the US, theyre working on it.

drinking last night were u?

We don't have enough prisons for everyone on this earth

The prisons would fill up rather quick, so we'd either have to build more prisons or put people on house arrest. Then, since everyone would be in jail, society would basically come to a halt as there'd be nobody working and maintaining life as we know it. 

Everyone, even prison guards.