First, I would recommend you to stay away from the term “tribe” as it carries a theoretical connotation associated with an outdated framework to understand the evolution of social complexity.

As for your question, the short answer would be that it has been an uphill battle to maintain their identity as Mayas. The independence of Mexico actually worsen the situation for some, because at least during the Colonial period they were able to manage their own affairs under the Republica de Indios. Once Mexico gained its independence, the criollos and upper class mestizos made it really hard for indigenous communities to thrive, to the point that it became illegal to print documents in native languages. After that, native communities slowly started to lose their land during the formation of fincas and haciendas.

After the Mexican revolution (1910-1921…) things became even worse because of the development of modern ideas of national identities. To make it short the point was to Mexicanize the “indio” and to celebrate the “dead indian” (basically the stone monuments), while disassociate the “living indian”. It wasn’t until 1985 that the Mexican government recognized all native languages as national languages. Even today, if you visit the areas, the focus is “how can we make the most money out them” which translates in the development of tourist attractions that do little to help the native communities.

As far as Guatemala, the situation is very similar; even though indigenous communities account for large portions of the population, they are often the most marginalized. Maya communities in the highlands of Guatemala especially suffered great atrocities during the Guatemalan civil war.

To me it is more like an appropriation of culture by modern countries that often argue to be the descendants of Mesoamerican cultures, while the real descendants are push out of the picture.