Question

What makes it particularly difficult to patrol the U.S. borders with Canada and Mexico?

It is not difficult to reach any stretch of either border, as both borders are heavily populated and developed.

Water covers over half of the border with Mexico, making it difficult to navigate.

Large stretches of both borders cross rugged terrain and lack developed roads or highways.

Both nations claim sole responsibility for patrolling the borders.

Answer 1

water covers over half the border with Mexico

Explanation: immigrants often use the Rio Grande to cross the border. This river is notoriously hard to cross due to the harsh water and high risk of drowning.