You can't really, think it needs to be game invite. I had the same problem at first, slightly annoying...
As for being in the US I don't think that would matter, and I haven't had any problems with ping at all.
Looking for some new players for our region on Europe East 4.
We have 2 cities so far and there are plenty spaces for new cities and expansion.
Would be nice to have more to join.
Our region is called Viridian.