Suggestion: Add Server To Guild Roster.
Servers really only matter for WvW guilds. As long as everyone is from the same region everything else can be done together.
Just because it’s only useful for wvw doesn’t mean it’s not worth adding. It’s also pretty low hanging fruit to add.
Plus the non-wvw guilds might see they have a lot of server overlap and might be willing to give it a shot.
You can see their home server on the achievements leaderboard if you want. Simply login and filter it by your guild.
I’ve joined a couple of guilds since I returned, only to find out most are not on the same server as I am.
Why don’t you ask your recruiter/inviting member before joining?
However, as others have said, it only matters for WvW.
I’m in one guild for which I’m the only member from my world (which, coincidentally, is currently in a WvW match-up against the guild’s primary). I’m also in a cross-world guild for raiding.