that makes you feel strong emotions, it can be drama, suspense, sadness, adrenaline or even horny if you write something sexy, whatever it is but they must be strong emotions, a good writer is a drug dealer
In Wish Fulfillment, I like it when it's about kingdom building and the author makes the protagonist create a utopia according to his or her political ideologies, while other countries with an opposing ideology are backward or dystopian.
Exactly America is very rigid when it comes to comic themes, I'll give you an example, sports ones: Don't you find it curious that some of the best basketball (Slam dunk) and boxing (Hajime no Ippo) stories were created in Japan, when they are not exactly a country that excels in those sports...