I think we'd all be very...ephemeral as a species. I know that the whole elf/fairy/magical creature thing is a bit of a stereotype, but I've always felt...faded, yet timeless and full of life much like the archetype. My moment in this world is deep yet fleeting, and it is there that I find eternity by not really fitting in. I'm sure most, if not all the INFPs, would agree with me.
So, appearance-wise, the INFP race would come off as delicate and distant and elegant beings, almost beautiful and ageless, but not in a forced way. It's just simply who we are, and others, especially more "established" races like the NTs, would find that a bit intimidating even though we're harmless. Our clothes would be simple flowing things that is unique to the wearer, changing to however he or she is feeling. If an INFP felt regal, it would be a gown fixed with stars. If broken, morning garb swathed in night. So strong are our emotions would be that we'd radiate them in a glow, maybe even levitate when at their strongest. After all, since when have INFPs ever wanted to conform to logic?
Think Galadriel; when she's her normal self, she's warm and approachable, if a little distant. But if she's angered, she goes all one-winged angel like when Frodo offered her the ring. That would be our defense. Although we'd normally appear childlike or peaceful, there's something strong deep inside that shouldn't be let out.
As for our government, I honestly don't think we'd really have one. We'd all be doing our own thing with those we're closest with, and should a conflict arise, we'd just try to cooperate and see what works best for anyone. Since we don't like foisting our problems on others, issues and conflicts would be contained.