What is one right only for United States citizens?

The right to vote in federal elections is indeed a right specifically reserved for United States citizens. This right is enshrined in several amendments to the Constitution, particularly in the 15th, 19th, 24th, and 26th Amendments, which collectively prohibit the denial of the right to vote based on race, sex, the failure to pay taxes, and age for those 18 and over, respectively.

While free speech and the right to a fair trial are fundamental rights protected by the Constitution and apply to everyone within the United States, regardless of citizenship status, they are not exclusive to citizens. The right to run for office, although it is typically associated with citizens, has specific requirements that include holding citizenship, but not all offices are restricted solely to citizens (for instance, some local offices may allow non-citizens to run). Therefore, voting in federal elections stands out as a definitive right that only citizens possess.