Building a border wall and banning refugees will not stop illegal immigration. 40% of illegal immigration comes from visa overstays. Furthermore, people will always be able to find weak spots in the border where they can sneak across. It is impossible to completely eliminate illegal immigration. We can reduce it, but not stop it.
The order to build wall on the Mexican border and ban refugees may stop Mexicans from entering the US illegally but just for a short period before the immigrants device other ways. It is not known when the wall will be constructed and who will fund it because Mexican have said they will not fund the project.
This won't even be a challenge for the most determined. The only thing that will happen is the fleecing of the American public, which will be forced to pay for a never ending, money pit wall that Mexico was supposed to pay for. Mexicans have enough traffickers to get them where they need to go.
Building a wall between Mexico and the United States will not stop illegal immigrants from entering our country. Most immigrants from Mexico do not arrive by crossing the border by foot or car. The majority arrive by plane, and a wall will not stop these people. People are willing to die to come in, and a wall will not be an obstacle.