Looks like this should have been designed as one dB with an [area] column in Table1. That way it is one simple query.
But if you can't redesign then how about this:
Select A, D, C from DB1.Table1 where @area = 'UK'
Select A, D, C from DB2.Table1 where @area = 'US'
Select A, D, C from DB3.Table1 where @area = 'ES'
Be One with the Optimizer