Historically the term 'Latin' referred originally to an Italic tribe under the rule of the Etruscan League, which conquered the Mediterranean and became the dominant race there. During the middle ages the phrase Latins was used interchangeably with Franks by Greeks, Arabs and other peoples outside the Catholic sphere to describe those nations within the culture sphere of the Roman Church
The term was revived after the Franco-Prussian war by the French government, which sought to create a Latin Union which would serve as a way for France to rebuild their global influence and counter pan-Germanic nationalism and the allied empires of Germany and Austria, while side-stepping Bismarck's diplomatic isolation of France.
The idea of a united brotherhood of Latin peoples stretching from Romania to East Timor and Quebec to Tierra Del Fuego enabled the declining French Republic to spread their informal power and influence worldwide while also building a directly-ruled empire in Africa and Asia.
The term Hispanic refers to such concepts as Hispanidad, which is the idea that the peoples who formerly comprised the Spanish Empire have a similar heritage and brotherhood
Holidays like the "Dia de la Raza" celebrates the coming of the Spanish to the new world, the conquest of the natives and triumph of Spanish civilization.
Usage by the US Census specifically directs these terms only towards the people of Spain and the Spanish-speaking nations of Latin America and their descendants in the United States.
Other Latin peoples such as Moldovans, Angolans, Haitians and others are excluded by the federal government.
Further complicating the issue is that the Dia de la Raza and Hispanidad/Hispanic identity is considered a racist white supremacist concept by blacks, natives and mestizo identitarians in Latin America, who say that the crimes of the Spanish are the reason for enduring poverty in Latin America. The US considers all of these people to be Hispanic anyway.