nothing wrong with America's LEGAL immigration system, it works very well for the most part and allows people in that are vetted, have medical clearances, and waited in line for years.
Everything wrong with the country's ASYLUM laws. They state anyone can apply to live in the U.S. on the basis of persecution, which is a vary vague term. They get a court date and get released in American society, not sent back to their place or origin or kept in a detention center (no room left). Repeal all asylum cases except those providing proof of extraordinary circumstances like imminent death at the hands of the government or political persecution, not ECONOMIC persecution (i.e. i'd rather work at Arby's than some Honduran coffee shop). The Mexicans that hop the fence or the wall don't do that system because they don't want to live in the U.S. forever, they just want to make fast cash and send it home; alternatively, they've been arrested before and can't apply for asylum on that basis alone. The wall will keep THOSE guys out. But it won't fix the 20,000,000 already here or stop the asylum abuse.