The Tlaxcallans continued to support Spanish Conquistadores in the further expeditions, including the war in Guatemala, the wars in North Central Mexico, such as the Mixton War, and I think that some may have even made it to New Mexico. Domestically, Tlaxcala remained a semi-independent state within New Spain, at least from an administrative perspective. They were also initially exempt from taxation, although this grant proved temporary. Eventually, Tlaxcala was absorbed into the Colonial administration. However, it remains a unified state to this day.

If you are interested in some further readings, you might want to check out the following sources: Florine Asselbergs, Conquered Conquistadores: The Lienzo de Quauhquechollan, a Nahua vision of the Conquest of Guatemala, Univeristy Press of Colorado: Boulder, 2008

Laura Matthew and Michel Oudijk (eds), Indian Conquistadores: Indigenous Allies in the Conquest of Mesoamerica, University of Oklahoma Press: Norman, 2007