Aside from emotional resentment of "foreigners" coupled with perceived native unemployment, is there really a problem that needs to be fixed here and will stopping illegal immigrant flow fix it?
It depends on which problem, and on the perspective of the person talking about it. There are a number of types of "illegal immigrants" (many of whom, by the way, technically are not "immigrants" within the meaning of the U.S. Immigration and Nationality Act).
We have people who enter the country unlawfully. These include people who
enter without inspection—that is, they sneak across a border—and people who enter fraudulently: for example, they enter as tourists or other short-term visitors but actually are intending immigrants, they enter under a false pretext as a spouse or prospective spouse of a citizen, etc.
We have people who enter lawfully, but whose presence subsequently becomes unlawful after they arrive. For example, people who enter under a visa or visa waiver agreement that does not permit them to work, but then accept a job offer. (Prospective employers are supposed to verify that foreign applicants are authorized to work in the United States, but those pre-hiring checks are often cursory and only the most blatant employer-violators are likely to be caught and sanctioned by the government.)
We have people who enter lawfully and simply
overstay their visas or the terms of the visa waiver agreements with their countries of origin.
There are also some special categories, the best-known of which is people who entered the country with their parents as young children and who assumed they were U.S. citizens or permanent residents—only to discover that they are neither. (These are the so-called DREAMers, a double entendre on the term "American Dream" and the acronym of a proposed law, the
Development, Relief and Education for Alien Minors Act, that Congress considered but never enacted).
All these people are technically subject to deportation or
voluntary departure (an administrative agreement by the foreigner to leave the United States by a specified date), even if they haven’t committed any crime. During the latter years of the Obama Administration, the government emphasized the removal of criminal aliens and tended to leave the rest alone. It's not clear to what extent the Trump Administration will continue this policy. Interestingly, two U.S. immigration agencies—the Border Patrol and Immigration and Customs Enforcement—issued a joint statement earlier this week saying they would not routinely target law-abiding aliens at evacuation sites, shelters, or food banks in the flooded areas of Texas.
