"But last year there were 540,000 people, roughly, detained coming across the border illegally. Forty-five thousand of them came from countries other than Mexico, demonstrating the fact that Mexico itself now is a pathway into the United States for people all around the world, and we don't know what their intentions are"

This quote by John Cornyn is referring to the number of people who were detained while trying to go across the US-Mexico boundary illegally in the previous year. He states that 540,000 individuals were restrained, and 45,000 of them were from nations apart from Mexico. This demonstrates that Mexico is currently being used as a pathway for individuals from all over the world to go into the United States. Cornyn is emphasizing the reality that the objectives of these people are unknown, and also this can be a possible security risk. He is most likely recommending that the US needs to take steps to better protect the border as well as guarantee that just those with legitimate objectives are allowed to go into the nation.