In our timeline, the Spanish and Portuguese conquistadors engaged in miscegenation with both the indigenous population and Africa slaves which resulted in the racially-mixed population in Latin America today.
But let’s say that in an alternate timeline:
1). The conquistadors bring their own women to the Americas.
2). The Catholic Church strictly prohibit miscegenation between whites and non-whites.
3). More massacres and smallpox epidemics happen.
4). Spanish and Portuguese authorities allow Catholics from Europe to immigrate to their colonies. Aside from more Spanish, Portuguese, and Italian families immigrating, many Dutch, German, and English Catholics immigrate to the New World as a result of the anti-Catholic sentiment arising due to the Protestant reformation.