How does geography affect morphological features of the human body
Geography does not typically affect the morphology of the human body.
In certain special cases, there are physiological adaptations, the most obvious being tanning and acclimatization to high altitude, but these aren't changes in body morphology.
So why the difference in children of immigrants?  This is because diet, nutrition, and disease have quite strong effects on children's growth. Kids growing up in a healthier environment with more food get bigger, and those are linked to the wealth of the community where you live.