A Tale of Two Cultures

Before going to America, I learned some American table manners. And then I held my first dinner party and even learned a new word:
B.Y.O.B
We had a wonderful dinner. At the beginning of the dinner, I welcomed them to my “cold cottage” and said sorry for “not treating you well”, as Chinese usually do, to show my humility. At the end of the dinner, everyone shake my hands and thanked me, as Americans usually do.
However, the next day, one of my colleagues came to my desk and thanked me again for the delicious food. I was a little bit surprised that he was so polite.
Then a strange thing happened.
My colleagues who attended my dinner came to my desk one by one and thanked me again. One colleague who did not go to office called me and thanked me again.
Do Americans always thank twice for a dinner?
“Not always,”my friend said:” Maybe they really like your food.”
But another friend said it is also one of the rules to double thank.
That night I could not sleep and kept accounting how many dinner parties I have attended and how many “thanks” I didn’t say.