what Other things can cause the chest X-ray appearance of hyper expansion/air trapping.?

Hyper expansion. COPD, asthma, cystic fibrosis and other cystic lung diseases, some infections(RSV), and spurious chest X-ray finding due to large inspiratory excursion.
Depends on age. Causes of air trapping in children different than adults. Less than year of age respiratory syncytial virus (RSV) and other viruses. Congenital emphysema, cystic lung & aspiration occur in infants. Acute .Asthma affects young childen, adolescents, and adults.Cystic fibrosis usually seen in children, adolescents & adults with improvements in therapy living much longer. COPD mainly adult.