Back in the early 80's, the runway at Auckland International Airport in New Zealand was upgraded so it could be an alternate for emergency shuttle landings. It's never been used for that purpose.

I believe there are numerous similar runways around the globe that are long enough, and have the capability to land a shuttle.

If the weather is bad at all three US sites, there are others.....but the cost of piggybacking the shuttle back to KSC would be a bit pricey!!

Cheers,
Phillippa