Almost always an appositive interrupts the flow of a sentence and is therefore set apart with specific punctuation. Appositives are set apart with commons.
Since appositives add additional information to a sentence, most appositives can be completely removed from the sentence and the sentence will still be grammatically correct.
Answer: She was reluctant to define anything remotely resembling a national character because " it was a mongrel nation." There were so many different ethnic groups that had merged into one. This made it difficult and sometimes pointless to make just one group "entirely American."
