FWIW, the Dota2 International[1] for 2018 will be held in Vancouver this year, all previous editions were in the US.

[1]: https://en.wikipedia.org/wiki/The_International_(Dota_2)

They could split the conference into an US and an EU branch, run simultaneously by streaming, so researchers could make their presentations and attendees watch from both countries. That would limit the mingling and interaction though. If your goal is to make contacts, find employees, investors or jobs, then you got to go through the hoops.