"Hispanic" is a fabricated ethnicity.
I have no common ancestry, social structure, cultural or national experience with these kids.
Nothing.
So how am I of the same ethnicity?
No argument with what you state. The census definitions were probably developed by government sociologists, in order to create a separate grievance category, for the purpose of dispensing benefits.
The category of "Asian" combines people that may look similar, but speak languages that are not alike.
I once had a good client that was a Japanese expatriate business manager. He had worked all over Asia and then the US, where he decided to retire. Highly educated, and quite a nice gentleman. He had served during WWII as an interpreter for American POWs. Loved and respected America and Americans.
He told me that the Japanese are very racist, viewing themselves as superior.
The tendency for mankind to identify with his own group, to assert its superiority, and to look down on "the others" seems nearly universal.
The influx of Irish in the 1800s was a clear situation of this. Irish were once called the "bleep of Europe." The term Scots-Irish is unique to America, used by colonial (1700s) era Irish immigrants to set themselves apart and above the recent 1800s influx. The colonials immigrants were predominantly Protestant, while the latter were predominantly Catholic.
Yet in fairly short time, the Irish Catholic immigrants overcame discrimination. The same or similar situations have occurred for Scandinavians (dumb Swedes), Polish (dumb Pollock) etc. Peasant Jewish farmers from Russia and Ukraine, in the Plains states.
Mexican Americans have different histories in Texas vs. California vs. New Mexico etc. My wife's parents came from fairly recent Italian immigrant stock, directly to California from one village in Italy, where she still has first cousins.
From colonial times family and neighbors came from "the same villages" because of letter to back home. The letters said "come on over, we're doing well, and so can you." The reasons were economic opportunity, political and religious freedom.
As virtually all groups soon overcome their initial "disabilities," save the blacks. The "great Society" set them up for the disaster of special treatment, diminished expectations, entitlement, destruction of traditional families etc.
My Latin looking wife took the man we bought our first home from, to small claims court, to force him to comply with terms of the purchase contract. He sat in court and called her a "dirty Mexican," but she won of course.
So race, ethnicity religious "differences" have been present across the globe, and remain strong forces. No sooner than the English colonists arrived in New England, did they start arguing over religion.
These "dissenters" left Europe for freedom of (their own) religions, only to try establishing dominance over other religions here.
