Apple Docs says:
Who can use Search Ads
If you’re a developer with an app currently on the app Store for iPhone or iPad in the U.S., or an agency that manages campaigns on behalf of developers, you may be eligible to use Search Ads.
Does it means only developers from U.S are eligible?
YES, currently only US registered developers have the feature access. (Rumours are it will be globally available after the March '17 event)