Final answer:
The most troublesome part of American existence according to de Tocqueville was the tyranny of the majority, which he saw as a negative consequence of democracy.
Step-by-step explanation:
For Alexis de Tocqueville, the most troublesome part of American existence was the potential tyranny of the majority, where the will of the larger group overpowers that of minorities and individuals. This concern highlighted deep-seated issues related to democracy that Tocqueville observed during his visit to the United States in the 1830s, as he analyzed the social revolutions and the rise of democracy.
He believed that while democracy had significant benefits such as equality before the law, it also brought about new forms of oppression, particularly towards those who are not part of the majority.