addition in datetime column during insertion in mysql
I doubt what are you trying can be done in a single go.You could do it specifying timezone for all inserts for a particular country.
Or something like this after insert:

UPDATE....
  CASE WHEN Region='India' THEN event_time = event_time+INTERVAL 330 MINUTE 
  CASE WHEN Region='America' THEN event_time = event_time+INTERVAL someother MINUTE
  CASE...