Wikipedia[0] has a short paragraph on the history and I'd say that any project involving so many different countries and governments (and bureaucracies!) is a red-tape hell.
Just choosing the location was a long and difficult process[1]. Canada proposed a location but later pulled out, Japan put a lot of pressure to get it built there. Even within Europe it caused a political "war" between France and Spain, both proposing different sites. First the EU decided to back France and it was finally agreed upon as the final location.
From what I remember, many people complained about the decision. Japan felt left out and was offered 20% of the research personnel. The infrastructures in France had to be built from the ground up even before the actual work to build the plant could start, the area didn't even have big enough roads to bring all the materials, which in turn delayed the works and increased the costs (something that wouldn't have happened in Spain or Japan, no idea about Canada).
[0] https://en.wikipedia.org/wiki/ITER#Organization_history [1] https://en.wikipedia.org/wiki/ITER#Location