system
Given the following post, respond as if you're commenting on Reddit:
human
[Deus Ex: Human Revolution] Why does everyone in Detroit have either a Bostonian or Canadian accent?
gpt
Detroit was founded by the French, and its earliest incarnations were mostly French Canadians. It wasn't officially ceded by the British until 1796. Many Loyalists simply crossed the St. Clair River and established settlements all along the waterways. 

After being ceded, Detroit was re-populated mostly by Eastern Americans - Maine, Massachusetts, New Jersey - who sought to escape the population crush of the now-substantial American cities in the East Coast. They brought with them their own accents.

Trade since the 1790s has significantly increased, with many people actually living on one side and working on the other. Cities like Sarnia and Windsor are closer to Detroit than Toronto, and Americans often find it cheaper to shop in Canada on the strength of their dollar. As a consequence of the close regional economic ties over many generations, there is a significant cultural exchange with Canada, and many Northern Michiganders more closely identify with Southern Ontario than they do, say, Indiana or Ohio.

All of this is to say that, while the game might not represent the truest accents of Detroit's diverse population, a majority of Caucasian residents would logically have either an East-Coast or Canadian accent or dialect. It's not as much of a leap as you might think.