What happens if don’t belong to any of the groups while setting a geolocation routing policy?
For queries coming from those IP addresses that Route53 cannot determine the original geolocation (i.e. no mapping that can be found), it will return a "no answer" response, unless you create a "default" record for such cases.
Geolocation works by mapping IP addresses to locations. However, some IP addresses aren’t mapped to geographic locations, so even if you create geolocation records that cover all seven continents, Amazon Route 53 will receive some DNS queries from locations that it can’t identify. You can create a default record that handles both queries from IP addresses that aren’t mapped to any location and queries that come from locations that you haven’t created geolocation records for. If you don’t create a default record, Route 53 returns a "no answer" response for queries from those locations.
More info at: Amazon Route 53 | Choosing a routing policy.