I believe you, but those lib voices aren't heard. They're only acknowledged during election time.
Since I know first-hand about illegal immigration in the US, the problem I see is identification and verification. Here is an example. When I was on duty, I stopped who I suspected was an illegal immigrant and criminal albeit it was for trespassing. He provided his driver's license as identification which I suspected was fake. However, it was good enough to pass the eyeball test. He was taken to the station and then later released. Being a Juan Garcia and his birth date wasn't enough to verify because there were too many in the database. If the guy was in the US illegally, then a fingerprint check would be able to confirm his identity but he had to have been arrested prior. A facial recognition would be able to track where he goes. This system would take time to set up and have to get past civil liberties complaints. If he is an illegal who has valid work and support, i.e. not a vagrant or criminal, then an identity could be made from that point on. He could be issued a work permit.
I am opposed to the wall because it's stupid. I do not want America who is supposed to be a world leader go back to the Middle Ages. It will take much work, but fingerprinting and taking facial recognition photos of everyone in the US would replace and modernize the concept. We aren't like Israel in the ME where a physical wall isn't necessary in case of attack.
As for sweatshops, that is why companies like Ford want to move their manufacturing there. The sweatshops exist because they can offer work and limited training for unskilled workers. It a cycle that becomes grueling for them because they cannot escape the cycle of poverty. The liberal universities and think tanks in the US have eliminated vocational studies requirements in high school because of the lack of manufacturing in the US. That is capital based trade. They want to force the US to go service based and force unskilled labor to do menial work that is required for farming, cleaning and maintenance here. Thus, high school has dropped them from their curriculum. Trump could stop this and bring back manufacturing to the US. This is one of the reasons why Clinton lost. She is a lying, cheating scumbag who should be in jail along with some of her supporters.