There's good things and there's bad. The good things can be that nations are at least getting together for one cause or one thing in common and are getting together for sports instead of waging war with each other. But then there's the bad aspect of it where the fanatics get caught up with the game and put too many emotions into it and so it leads to violence, political conflicts or whatever else usually happens at such events. I don't think it's a bad thing to be patriotic and support your country, but of course it gets out of hand.

Well I think it depends on the country.  The world cup in Europe (football generally) seems to lead to a lot of anger between fans.  At the Asian games, Chinese fans end up making lots of anti-Japanese statements...
My opinion is that nation-based competitive sports doesn't improve international relations at all...  People get very nationalistic.  

probably. we see and learn that people from other nations are just like us. the see that we are just like them...