How did Mexico become a federal republic?

Answer 1

When Mexico acquired its independence from Spain, it originally became a monarchy, led by Agustin de Iturbide (Agustin I of Mexico). He however, was a bad ruler with constant scandals and wasteful expenses.

In 1823 some generals led by Guadalupe Victoria and Antonio Lopez de Santa Anna formulated the Plan of Casa Mata, which abolished the monarchy and established a republic. During the following months, most provinces adhered to the plan because they agreed to be part of a federal republic, as much like the former British colonies in North America, they would remain independent but could be part of a federation.