Answer:
The improvement of agricultural methods allows for cheaper food produce which in turn makes sustaining cultural traditions with food to be affordable and as a result, the cultural expansion is easily tracked by cultural food traditions being correlatively popular in countries other than their origin.
Step-by-step explanation:
I'm not an expert on the subject however, I have a great memory, and still remember information behind this, however its best in this subject to use the information provided, as its a complex subject with not just one answer.
Background:
We see in history back when there was little exchange that food cultures have developed independently. However come around the cultural exchange you start to see a diffusion in foods people eat originating from other cultures. This is the first case of it, however its not the big aha of the subject because it was still quite limited by the price of foreign grown foods. Like rice wasnt really grown in europe, meaning only the rich could afford foods from other cultures.
However, come the age of improved farming where we have surpluses of everything, it was affordable to sustain food traditions. This is where the question is most likely referring to. As a result of this surplus in food, the foods grown in other countries were cheaper and thus could affordably follow the people sustaining their cultural traditions regarding food in other countries. This is much more prevalent in America, the most culturally diverse country, which just happens to be the largest exporter of cultural foods in the world.