system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is building a fence/wall at the U.S. border considered foolish?

I see this every once in a while.  Why is this a bad idea?

-Non US citizen.
gpt
Because the border is fucking HUGE. Seriously the border of the US and Mexico is almost 2,000 miles; for a comparison the entire border of France is ~1800 miles. Also it is just a fence and people can easily jump it like they do now where fences are in place. 

And it will cost a shit ton, not only to build but to maintain.