What role does the growth of population play in O'Sullivan's ideas about "manifest destiny"? How does he explain Texas's break from Mexico? Why does he predict the eventual separation of California?
How would you describe O'Sullivan's views of race? In what ways is "manifest destiny" for him tied up with his belief in the superiority of "Anglo-Saxon" peoples?
I assume that you are asking about O’Sullivan’s 1845 article “Annexation.” I will answer with reference to that article.
For O’Sullivan, the idea of Manifest Destiny was inextricably tied to the idea that Anglo-Saxons were superior to other “races.” When O’Sullivan is talking about how California will inevitably separate itself from Mexico, he calls Mexico a country that is “imbecile.” He then goes on to contrast this with the Anglo-Saxons who were settling the American West and bringing with them
…schools and colleges, courts and representative halls, mills and meeting-houses.
In other words, Anglo-Saxons are superior enough that they bring with them the benefits of civilization where Mexico, with its population that is not Anglo-Saxon, is too “imbecile” to do so.
O’Sullivan says that California will separate from Mexico because Mexico has not been able to exert control over it or to put a population there. By contrast, the United States has been able to put people there who are ready to populate and civilize California. The same goes for Texas. O’Sullivan argues that Texas was populated by Americans. The Americans had the right to separate from Mexico because that country was trying to “enslave” them.
So, O’Sullivan thinks that Texas and California will naturally belong to the US because it is Americans who have settled them, with their superior civilization that comes along with being Anglo-Saxon.