The greatest wall of all time was a failure. The Great Wall of China did not prevent invasion. A border wall with Mexico will not prevent whites in the United States from becoming a minority.
A wall is high cost and low benefit. It is high initial cost and will still require manpower and maintenance in the long run.
Money is better spent on infrastructure that supports the long term needs of the country. Cleaner energy, bridges, tunnels, water treatment, technology and science.
A border wall is simply a mob reaction to problems created by tax policies that have failed the many and benefits the few. Mobs don’t understand that because they are simple minded and emotional.
Cost benefit analysis should always help guide spending decisions.