“Or by Missouri's rushing waters laid” (line 92). In her work Eighteen Hundred and Eleven, Anna Letitia Barbauld uses an allusion to the rushing waters of Missouri to show that it is unstable, a fact continued by the rushing waters as well as the major earthquakes happening at the time.

here is another image of the hurricanes.

Missouri was a territory in America, which she is critiquing as a product of imperialism and wonders if it (as part of America) will eclipse Britain. 

Historically: in 1811-1812, there were the New Madrid Earthquakes. This caused upheaval and insecurity. The first establishment in Missouri was in 1700.