@Jeh ****
They end up at the Federal Reserve in the USA that exchanges them for new.
But the issue, half way across the planet, is getting them there. Maybe foreign banks have an agreement with a Western Bank or perhaps they use a special courier.
But the issue is also time and expense to exchange them. They cannot just reuse them in Asia right away.
But don't worry, they don't lose $100 for a torn bill. But there is a cost to them via money and/or time.