International wires are supposed to take a few days—if a wire is delayed for weeks or a month, where is the money during that time?

The money is most-likely temporarily parked with some institution where the problem or issue may be.

See the diagram below:

If the payment origination starts at Bank A and terminates at Bank C (in this simplistic example), then the payment is like a flow, (from A to C). When you pause the flow (which is what you are defining), then depending where in the payment cycle we were, the money will be sitting in one of the three banks, awaiting further action.

Image Credit: Distributed Ledgers in Payments: Beyond the Bitcoin Hype