Why was not okay for William walker to conquer Nicaragua?

William Walker's conquest of Nicaragua in the mid-19th century was problematic because it represented a blatant act of American Imperialism, undermining the sovereignty of a sovereign nation. His actions were driven by expansionist motives, seeking to establish a pro-slavery regime, which further fueled tensions over slavery in the United States. Additionally, Walker's regime was marked by violence and oppression, leading to significant suffering for the local population and exacerbating political instability in the region. Such interventions are generally viewed as violations of international norms and principles of self-determination.