How does geography affect U.S. border security?
The United States of America is bordered by the Pacific Ocean to the West and the Atlantic Ocean to the East. The two water bodies provide natural entry barriers to the United States because the entire stretch of the coastline is easily manned by the Coastguard and other authorities. Ships and smaller boats are easy to spot, and those that arrive officially are checked at the different ports. The setup makes entry through the waterways highly unlikely for illegal immigrants due to the high risk of getting caught.
The United States borders Canada to the North and Mexico to the South. The borders between the different regions consist of huge swathes of land with parts of forested areas. The terrain makes it easy for illegal entry; however, Canada, as a developed nation, controls its borders better than Mexico and the capacity to adequately secure the border with Canada is well coordinated with the United States authorities. Mexico, on the other hand, does not deploy enough resources to secure the border, and the United States is left to struggle with the high number of illegal immigrants trying to crossover from the south in search of better opportunities. The geographical terrain and the economic condition of its southern neighbors make it difficult for the United States to adequately secure the border and prevent illegal entry.
Geography affects American border security by making some borders easier to cross and/or more likely spots for illegal crossings while making other borders relatively difficult to penetrate.
For the United States, the East and West Coasts are relatively difficult to penetrate due to their geography. They face onto large oceans and are mostly quite far from any foreign countries. By contrast, the northern and southern borders are very long land borders. They go through very remote areas and can be very hard to patrol. The northern border, though, is typically seen as a less likely spot for illegal crossings because it borders on a rich country as opposed to a relatively poor one. In these ways, geography determines which US borders are most likely to be crossed illegally.