Honestly, the immigration issue is a multi-pronged problem. The first part of the problem (and the reason why there are many more people trying to come over the US-Mexico border than the US-Canada border even though the US-Canada border is 2-3 times as long with probably less than 1/10th the border guards) is that Mexico is a much poorer country than the US, as far as median income is concerned. This part of the problem is Mexico’s to fix, and if it’s not fixed, then the immigration issue won’t be, either. We could build fences, lock down the border, etc. - but people desperate for a better life (especially the life in the US that’s displayed to them on Mexican TV) will take desperate measures. Increased security, in my view, will only slightly slow down the traffic of people trying to get into the US. This isn’t to say it shouldn’t be done, but… the biggest impetus for Mexican immigrants returning to Mexico the last few years was the economic downturn in the US. They couldn’t find work, so they went home.
This leads into the second problem. There are many employers (most notably in the construction and agriculture trades) that willfully ignore their employees’ immigration status. In fact, many in these fields deliberately hire people who don’t have documents! In agriculture, the wage is set so low (it’s often based on bags filled instead of an hourly wage) so that very few American citizens would even touch the job. The agri-businesses don’t care, because there’s plenty of undocumented workers who jump for joy at the opportunity, and who won’t complain of poor wages or poor working environments (this is why Cesar Chavez railed against illegal immigration - the undocumented immigrants were preventing American farm workers from getting a safe working environment by being the “scabs” that the agri-businesses used when the United Farm Workers went on strike). And in states that have cracked down on agri-businesses that hire undocumented workers, such as Alabama and Georgia? Crops simply spoiled because the agri-businesses refused to raise their wages to a wage that Americans would work for. As for construction businesses, many contractors hire undocumented workers so that they can cheat in the bidding process. Undocumented workers = less pay that needs to be paid to the workers. Less pay that needs to be paid to the workers = lower bids. Lower bids = more opportunity to win bids. Regardless, as long as companies are willing to hire undocumetned workers, people are going to try to come over.
The third problem is this - Americans are generally unwilling (and some are unable) to pay for the increase in price that would come to groceries, especially, if the immigration laws were toughly enforced. I think, actually, that this is the reason why the GOP insists on “more border security”. They know that it’ll gain votes (just as Dems insisting on a “pathway to citizenship” will gain votes), but, when push comes to shove, they’re simply not willing to pay the money to improve the security. It’s also why the GOP is against a pathway to citizenship for undocumented immigrants - as soon as undocumented immigrants gain legal status or citizenship, they might insist on better pay and working conditions.
The fourth problem is simply - it’s quite difficult to come to the US legally, especially for unskilled workers. Work visas need proof of employment. Student visas need proof of enrollment in an educational institution. Even tourist visas require that the person show that he/she has a certain amount of money. As for resident alien (“green”) cards - they need sponsorship by either (a) one’s employer or (b) an adult relative who is also a citizen of the United States. As such, it’s actually easier, in many cases, to come over illegally and then legalize one’s status later.
Regardless, there are some undocumented immigrants that commit crimes. Many Mexican gangs straddle both sides of the border - pushing drugs here, then sending the money back to Mexico to buy military-grade weapons and terrorize Mexico. There are undocumented immigrants who blantantly ignore the laws in the US (including laws on drinking when driving) and many who ravage areas near the border. Those who wish to demonize people without legal status in the US point to these criminals and use them to condemn all who are here without papers. But - remember this: the number one brain surgeon in the United States came, originally, as an “illegal” immigrant, crossing the fence separating Mexicali and Calexico.
. Or is that one of those Southern “Bless your heart?” 
