Which countries are easiest to gain rating points and earn FIDE titles in? I recently played in a tournament in Iran (Fajr Cup, u2000), where 1600-rated players were a serious threat, and 1400-rated players would fight to the last pawn.  I don't think a single opponent of mine made significant tactical errors--they know how to calculate.  In my opinion, these players are vastly underrated, maybe by 300+ rating points.  I also play in China, which is also considered an underrated country (but Iran seems more underrated).

Players suggest countries for relatively easy rating points and FIDE title norms: A WGM suggested France or Spain, and a WFM suggested Turkey to me.  I'm tempted to go norm hunting, but I wonder where.

Question: Which countries are easiest to gain rating points and earn FIDE titles in?

I'm after something a bit more concrete than some random countries, e.g., the usual places players go to get rating points and norms.
Rating is a lagging indicator. That is, it gives an estimate of playing strength in the past. Therefore by definition players who are improving are underrated and players who are declining in strength are overrated.

Therefore as a first step if you can enter late you should look at the age profile of the entries and avoid entering tournaments with lots of very young players (who are likely to be still improving) and try and enter tournaments with old (preferably senile :-)) players (who will likely be on the decline).

Looking at the raw FIDE rating data which FIDE supply from January 2019 (I haven't yet loaded the latest February data in my database) and running a query gives the following results for average Date of Birth year for active players in federations with at least 1000 active players -

P 1. Denmark - 1966.4
 2. Netherlands - 1969.5
 3. Switzerland - 1970.95
 4. Finland - 1972.8
 5. Austria - 1974.2
 6. Germany - 1974.6
 7. Serbia - 1974.8
 8. Sweden - 1976.1
 9. Ireland - 1976.2
 10. Bosnia Herzegovina - 1976.7
 ...
P 22. Spain - 1984.9
P 23. Australia - 1985.2
 ...
P 34. France - 1986.9
 ...
P 56. Iran - 1992.6
 ...
P 70. India - 1997
P 71. Turkey - 1997.8
 ...
P 76. China - 1999.2

So, for best results try and enter tournaments in countries at the top of the list and avoid countries at the bottom.

Note that Spain and France are not much different to Australia and Turkey is on a par with India - far too young!