In Europe, where history has proved that domestic threats can be devastating, freedom of speech comes with certain caveats.

Key differences: “Incitement to hatred” is a crime in Germany, and in France, the act of publicly denying the Holocaust or other crimes against humanity is an offense.

In the U.S., on the other hand, hate speech is not regulated, and is not routinely removed from social media. There are some speech restrictions — journalists, for instance, must routinely work within the bounds of libel and defamation laws. But tragedies like the one in El Paso have reopened a debate around those limits.

Global reaction: The world responded with shock to not only the ubiquity of guns in America but also the rise of white nationalism. For example, the newspaper El País in Spain framed the El Paso shooting as the “greatest racist crime against Hispanics in modern United States history.”

Some nations, like Uruguay and Venezuela, even issued travel warnings for the country.

Gilroy shooting: The F.B.I. has opened a domestic terrorism investigation into the shooting last month in Gilroy, Calif., in which three people were killed.