An engineer describes the complexity of building a 1,900+ mile wall

Leaving aside political questions(which are important), He implies that it is very hard to build a wall. Not true.

Israel, a tiny country, much poorer than the US build a 440 mile wall.Other estimates talk of a cost of building that wall between $15B-$25B. That's not that big of a sum of a country the size of the US.

Will the wall work ? the wall in Israel did have a significant impact on terrorism, at least from my understanding as an Israeli.

EDIT: if you downvote, please explain why.