This may be the #1 reason why NA+EU strategus can't work:
NA gets booted a lot from the EU3 server.
I've been booted twice four times ("connection to the server is lost") during the Dhirim siege and now the EU3 server doesn't show on my list (nor do any of the EU servers).
Eventually it will come back but it would be hard to have a serious EU/NA game when we can't reliably connect or stay connected to each others servers.
This has happened during other battles in the past as well. I don't seem to notice it on EU1, just EU3. Maybe it's an issue related to population. There were 140 people on, which is more than other servers typically allow. (However, I can't recall ever getting booted from NA3.)