If you want to know why Northern New England is the most Anglo (non-hispanic white) part of the country, a great map from Vox explains it.
The map shows the top country of origin for each state at each dicennial census. In 1850 and 1860, Ireland was the biggest source for New Hampshire; since then, we along with Vermont and Maine have had Canada as the top source of immigrants. That’s no way to get an ethnically varied influx! Even Massachusetts has been more varied – Portugal pops up once, and in recent decades it has been China, which for this definition includes Taiwan.
You can see the map right here. Vox has a history of making interesting maps that explain interesting things – they are well worth exploring.