A U.S.-Mexico border wall is a wildly expensive showy publicity stunt that won't stop illegal immigration, but will likely cause the smuggling cartels to double their prices. Trump wants $18 billion over 10 years, so he can build about 350 miles of new fencing and rebuild another 450 miles. What a bad investment. Here's a better way to spend just a fraction of that in a way that might actually do some good.