Wouldn't be the first time; the Japan/South Korea World Cup featured a hard border, and almost as much underlying enmity as a post-Brexit UK/ROI one would.
Bugger me, 2030, thought I'd had one of my long naps there. Oh, single country hosting please, and no slave labour this time.
You do know that countries have always had borders and people still managed to have holidays and travel through them....open borders between EU countries is a relatively new thing.