There was a brief outburst of anti-immigration sentiment in the late 1790s as a belated response to the threat from revolutionary France. This found expression in the Alien and Sedition Acts of 1798, which, among other things, extended the waiting period for naturalization to fourteen years. It was reduced again to five in 1802.
Immigration was slowing down in any case during the 1790s, and in the Napoleonic period became a mere trickle. It would remain low until 1832. Americans did not seem to be concerned by the drop-off, perhaps because their natural birthrate was so uncommonly high. Some of the founders may have been influenced by Montesquieu’s idea that republics require an especially high degree of social homogeneity. Jefferson, despite his earlier protestations to King George, became concerned that immigrants would “bring with them the principles of the [monarchical] governments they leave, imbibed in their early youth,” thus weakening the republican spirit.
Many were also reluctant to see the young republic riven by ethnic conflicts. Hezekiah Niles, Baltimore publisher of Niles’ Weekly Register, was generally a pro-immigration voice, but expressed the following reservation:
If a citizen of the United States, born in England, Ireland or Scotland, is a candidate for office, the custom too generally is for all his countrymen to support him, thereby maintaining an interest separated from that of the people at large: and in some of our public offices also, when the head of it happens to have had the place of his birth in a foreign country, we find that nearly all of his subordinates are of his own class. This sort of clannish spirit begets one of opposition, lessens the public liberality, and militates against the public harmony… Their conduct is highly indelicate, and a very improper return for the courtesy extended to them in permitting them to elect and be elected to office.
[…] Lingering foreign loyalties continued to arouse suspicion. In 1856 the U.S. Government brought action against a dozen Irish-born naturalized Americans for membership in a secret society pledged “to uproot and overthrow English government in Ireland.” The men were said to have violated an 1818 law prohibiting the preparation of any military expedition or enterprise against a state with whom the United States are at peace. The presiding judge sternly warned the defendants “there can be no such thing as a divided national allegiance.”
(The Social Contract, Vol. XX, No. 2, Winter 2009/2010).