In OTL, there was a large number of people from Germany (dubbed the 1848ers) who emigrated from Germany following the failure of the 1848 revolution. Now, assuming the revolution succeeds, these people wouldn't have an incentive to emigrate to the United States. It should be noted that there was a fair number of politicians, journalists. Also, many of the 1848ers fought in the American Civil War. How would the United States have developed without the 1848ers?
And conversely one must ask, what would be the long-term ramifications in Germany?