How do airlines choose what food to serve?
1. Money

Meals are available at different prices. Most US airlines know you aren't choosing them on the basis of cuisine and pick the lowest priced meal they can get away with. Other airlines eg Emirates, Singapore compete by offering high customer services and so invest more money in better food and service.

2. Culture

Airlines which are mostly flying a home market will adapt the food to the traditions of the country. EL-AL aren't going to be serving bacon cheese-burgers and Air India used to do very good veggie curries.