Are iphone 5 already sold unlocked in the us?

I intend to use it in other countries

No. Three major companies make the iPhone available. Two of them can't be used outside the US on foreign networks (Sprint and Verizon) because they are CDMA carriers and the devices are not compatible with GSM networks.

The other major carrier is AT&T, which is GSM, but their cellular frequencies are often different from those in other countries, so even getting an unlocked iPhone branded to their company doesn't mean it would work outside the US (not for high speed data, anyway). They don't sell them unlocked anyway.

This isn't to say you couldn't buy one from some third party, but, again, there's no guarantee it would work on your network.