The meaning of each of the unKosher animals: Surely it means not to take part in the sins of the gentiles rather than the gentiles themselves? After all, there were gentiles in the Torah that were allowed to be joined to the Jews, such as Ruth.
I don't believe that specific animals must be linked to specific nations. One possible explanation. "Chewing the cud" represents the importance of food as nourishment rather than satisfaction of desire alone. "Split hooves" represent the limitation of violence.