Illegal border crossings in the US are currently at historic lows and major improvements have been made in the last couple of decades in this area already. Meanwhile, about half of the current illegal population is not from illegal border crossings, but people overstaying their VISAs. This problem, unlike the border, has not subsided and continues to be a major problem. As such, in recent years, the number of newly illegals in the country has exceeded illegal entries since 2007 and overstaying is more around 60-80% per year now. The border wall is a massive virtue signal aimed at the wrong part of the problem, similar to Voter ID, abstinence-only sex education, public school "indoctrination", etc. It does have the benefit of showing off like you are doing something massive (and expensive) and sounds like common sense. Unfortunately, it misses the point entirely and is another case of conservative ideology favoring feels over reals.