Indonesian volcano changed the political landscape in Europe
SUPERVOLCANO TAMBORA’S ERUPTION LED TO “THE YEAR WITHOUT A SUMMER”
Tambora played a role in famine and epidemic outbreaks in Europe beginning in 1816. The ash ejected into the stratosphere affected crop failures for up to a decade after the explosion in far-away Indonesia.
The Tambora eruption nearly a third of a world away in Indonesia was 10 times greater in ejecta shot to the stratosphere than that of better-known Krakatoa. Climate experts believe that Tambora was "partly responsible for the unseasonable chill that afflicted much of the Northern Hemisphere in 1816, known as the 'year without a summer'."
In their book, 1816 - The Year Without Summer, William K. and Nicholas P. Klingaman suggested the frigid, wet weather that caused famine and inflated epidemics in Europe (and the northern United States) in 1816, continued for several years before the region slowly returned to climatic norms for that century.
Continuing economic factors would have affected Germany for the greater part of the decade from 1816-1825. Hardships over such a long period would have made starting over on the North American continent easier to consider, just as the potato blight increased emigration from Ireland in 1845-1852.