The correct answer to this open question is the following.
The refusal to accept New Mexico as a state says a lot about what people at that time thought it meant to be American. Thet showed a racist behavior because the United States Congress did not accept the New Mexico's application to be a state of the Union. The reason? Congressmen had many doubts about the kind of people -mostly Native American Indians- that could be part of the United States.
Yes, I see contemporary parallels or similarities with present events. Recent racists events have taught us that racism practices are very ingrained in some parts of American society.