Answer to Question 1
Possible reasons include: The high level of immigration to the United States and Canada from countries all over the world has enriched the cultures of these countries, as many immigrants brought traditions, languages, and cultural styles with them.
The native people who live in Canada and the United States have also added to the diversity of these countries.
The declining levels of discrimination based on gender, race, and sexual orientation have added to the cultural diversity of North America.
Answer to Question 2
Great Britain and France dominated Canada, and the major colonial powers in the Unites States were Great Britain, Spain/Spanish Mexico, and France. Greenland is not specifically mentioned in the question, though the book covers it, so it would not be incorrect to mention also that Greenland was dominated by Denmark.
Some of the impacts of the colonial beginnings of North America can be seen in the linguistic, cultural, and political systems that are in place today. Canada's Commonwealth and parliamentary political system is a result of Canada's colonial heritage, as is Canada having French and English as its two official languages.