This is probably the most wrong thing you've ever said here.
You really should read up on American History 1845 thru the Civil War.
It was a turbulent time of change. The nation was expanding at break neck speed, with the German Revolution of 1848 and the Irish Potato famine of the late 1840s, brought yuuuuge number of new and different peoples.
The Nativists were not happy.
https://en.wikipedia.org/wiki/Know_Nothing
Former president Millard Fillmore became a member and ran again as president under the Know-Nothing Party.
Along with consolidating former Mexican territory and the attempted expansion of slavery. A few years later the passage of the kansas-Nebraska Act. That separated us even more. David Atchison was absolutely sure the abolitionists would go to Nebraska and slaves to kansas. Bleeding kansas.
This country was still a maze of Virginians, Ohioans, Missourians, etc before being considered Americans.
This country did not unite until AFTER the Civil War as Americans. And a great part of that was the acceptance of all these immigrants that contributed to the war effort to preserve the Union.
Those Irish and Germans came to the US. They didn't want any other new country.
The Fighting 69th became legendary
https://en.wikipedia.org/wiki/69th_Infantry_Regiment_(New_York)
It was the German immigrants of St. Louis that kept Missouri in the Union.