Here's a WIP list I created of every currently reigning monarch:
THE AMERICAS
California: Ramon IV (2002)
Mexico: Agustin V (1999)
Cuba: Alfonso Fernando II (1997)
North Haiti: Michel (2002)
Santo Domingo: Isabel III (2010)
Peru: Luis II (1989)
Brazil: Pedro V (2007)
Argentina: Juan IV (1999)
EUROPE
UKE: Elizabeth II (1952)
Maryland: Benedict II (2018)
Acadiana: Jerome IV (2017)
Netherlands: Willem IV (2013)
Belgium: Charles IV (2009)
Luxembourg: Henri (2000)
France: Jean IV (2019)
Catalonia: Joana II (1977)
Portugal: Joao VIII (2002)
Benevento: Frederick Auguste (2003)
Switzerland:
Liechtenstein: Hans-Adam II (1989)
Nordic Federation:
Denmark: Margrethe II (1972)
Scania: Valdemar V (1991)
Sweden: Victoria (2018)
Norway: Harald V (1991)
Finland: Väinö II (2002)
Estonia: Gustav III (1994)
Austria: Karl V (2011)
Croatia: Tasilo (2011)
Montenegro: Nikola II (2011)
Albania: Leka II (2011)
Armanonia: Avram II (2006)
Greece: Konstantinos II (1966)
Bulgaria: Aleksander IV (1967)
Rumania: Viktor II (1999)
AFRICA
Morocco: Mohammed VI (1999)
ASIA
Japan: Reiwa/Naruhito (2019)
OCEANIA
Tongo: Tupou VI (2012)
Hawai'i: Kūhiō II (1995)
Update Log
3/14/2022 at 8:15 AM: Added Hawai'i, Morocco, and Tongo.
3/10/2022 at 7:05 AM: Added Albania, Armanonia, Benevento, Liechtenstein, and Montenegro.
3/8/2022 at 6:13 AM: Added California, Maryland, and Mexico
3/7/2022 at 11:04 AM: Added Acadiana, Argentina, Bulgaria, Croatia, Cuba, North Haiti, Peru, and Rumania.
3/6/2022 at 6:03 PM: Added Austria.
3/6/2022 at 3:54 PM: Created Post.