Quick fix is to rename the fields in 1 table, or move the columns from both tables into a new table and link to these with a unique key. These quick fix suggestions are probably not the proper answer but will get rid of the synth key.
You need to review the context of your fields used for say country i.e. ship vs employment country, etc. and see how that should really fit in on your data model.
Actually the concat suggestion above is probably a nicer quick fix