The colonial Sephardic history of Mexico is unclear. Possibly some former Jews participated in Hernán Cortés’ conquest of Mexico in 1519. Bernal Díaz del Castillo reports that several soldiers were executed for practicing Judaism. We do not know if these were genuine cases, isolated cases, or indicative of a trend.
Spanish migration to Mexico began in 1530. New Christians (people descended from Jewish converts) were officially banned from travelling to the Spanish Americas. No doubt some did, but presumably with forged documents which makes tracing their Iberian ancestry close to impossible.
Between 1492 and 1580, the year Spain annexed Portugal, the Spanish Inquisition had largely eradicated all vestiges of Judaism in their territory. Is it possible that some die-hard ‘secret Jews’ travelled to Mexico? Yes. Is it likely? Why would they risk discovery and embark on a long and dangerous journey to a jurisdiction where the Inquisition also held sway rather than taking the shorter journey to join a Jewish community in Europe or around the Mediterranean.
There are individuals and communities in Mexico who believe they are of Sephardic origin. I do not know what evidence is available, and anyway it is not for me to judge. The waters have been muddied by people propagating the nonsense that certain (or most) Iberian surnames are of Sephardic origin. Also, an activist self-styled bnei anusim movement in the southwest United States can be intolerant of those asking for evidence.
The claim that a secret community of ‘crypto-Jews’ from Mexico migrated to New Mexico is made by Dr Stanley Hordes in his book, To the End of the Earth. The evidence presented in the book for such a migration does not meet accepted genealogical standards, although this does not exclude the possibility of such a migration. Obviously there were people who migrated from what is now Mexico to what is now New Mexico, and there is some genetic evidence of shared ancestry between some people in New Mexico and some Sephardic Jews, but we have no way of knowing the migrants’ religious beliefs. The Jewish origins theory was challenged by an ethnographer, Judith Neulander, who was then subject to significant abuse.
We know that Portuguese New Christians settled in Mexico and, especially after the Portuguese revolted against Spanish rule in 1640, caught the attention of the local tribunal of the Inquisition. The Inquisition did not formally establish a tribunal in Mexico until 1571. Unfortunately many Mexican records, including Inquisition records, were taken to the United States where they were lost in a warehouse file. Surviving documents are in the collection of the Archivo General de la Nacion, in Mexico City. There will also be correspondence and some copies of documents in the Spanish archives.
The processo of the trial of Gabriel de Granada has been transcribed and translated into English.
Much later Sephardim from elsewhere, including Syria and Dutch and British Caribbean islands, settled in Mexico. If you descend from one of these groups and want help researching your genealogy, including for a Portuguese nationality application, then please get in touch.
What is you do not have a clear link to a diaspora synagogue community, but believe you have distant Sephardic ancestry? I am not the person to help. I suggest researching back through Mexican civil, Church and other records to see if you can find some accused by the Inquisition of ‘judaizing’ or who was Portuguese (pre-1750), or if you can trace back to Spain and find a New Christian ancestor there. These would be starting point at which you want to speak with a Sephardic specialist. Now, if you need help, it will be from someone familiar with Mexican archives including Church archives, and ideally able to visit them. Honestly, I have never heard of anyone who has proven Jewish ancestry this way. Perhaps a DNA test is another route. That may show ancestry shared with Sephardim, but will not tell you what an ancestor may have believed at any specific point in time.
A group in Israel is now alleging that maybe 100 million Latin Americans have some Sephardic ancestry, and presumably many or most of these are in Mexico. Is the claim credible? In the colonial period an estimated 1.86 million Spanish colonists migrated to Spanish America. Presumably the indigenous population was significantly greater. So, how many New Christians? It has been estimated that the global population of New Christians at their largest number was probably around 50,000. How many of these might have settled in Spanish America? A figure of 2,000 seems extremely high. What about the families of converted Jews in Spain between 1492 and 1580 who wanted to maintain a Jewish identity? The community that the Inquisition found to have largely disappeared? How many of them? I don’t know. Maybe another 2,000 is generous. So we have an estimated community of maybe 4,000 ‘Jews’ is a population of millions of others. It is statistically possible that they may have hundred of thousands or millions of descendants today. How meaningful if one out of thousands of ancestors was Jewish? Does that negate other ancestors who were ardent Catholics, followers of Aztec religions, or maybe Muslim?