It is permitted to eat the food of non-Muslims, even those who are not People of the Book, though it is (in itself) superior to avoid when reasonably possible.
When need arises, such as business, da`wah, maintaining neighborly relations (which is strongly emphasized in the sunna), and so on, it is not blameworthy, but one should take reasonable precautions that the food is halal.
In the West, we have the duty of spreading the light of Islam. The way to do this is simple: follow the sunna. The Prophet (Allah bless him and give him peace) used to be very careful about fulfilling the rights of his neighbors, even non-Muslim ones, and all those with whom he had dealings. He would send food, visit them when they were sick, and so on… The Prophet (Allah bless him and give him peace) is a mercy to humanity as a whole, not just for Muslims. True followers of the Beloved of Allah are the same.
Similarly, one should invite non-Muslims to one’s house for food, as food (being the most basic of human needs) has an amazing way of opening hearts and minds, without the need to be “preachy.”
We have to distinguish two matters: we should have good relations and ties with everyone; we should keep the regular company of believers.
And Allah alone gives success.