The best answer for this sentence depends on contexts and people envolved, atlhough it may be interpreted at a philosophical level in terms of how borders are responsible for making people to cross them; instead of people just crossing between places, they cross borders and these borders may cross them as well.
Explanation:
At a philosophical level it is possible to understand this sentence in the meaning of borders crossing people because they are not an option for people to cross, they are mandatory and, therefore, become responsible for dividing people and cultures. Gloria Anzaldúa is a chicana philosopher who states this context in her book "Borderlands/La frontera: the new mestiza" (2000) in order to explain the fact that chinano borders cross people who live in-between places and cultures, such as those of North America and Central America, and then make up part of their lives and identities.
I think the best explanation for this sentence can vary. If you're looking for an explanation on this sentence via current day situations I'd say its about the social injustice and camps being held at the border of the U.S right now. In other terms it could mean that "we" didnt initiate it, but it came anyway.
