There are a number of policies in place and proposed for immigration along the Mexican-US border. These policies have been developed over decades by both of the dominant political parties. For instance, Obama was known as the "deporter-in-chief" by those affected by his immigration policies that had deported for people than any previous administration. Today, Trump's deportation numbers may be lower, but he seeks even harsher policies that make achieving legal and undocumented access into the country much harder, has set up what amounts to concentration camps and a standing military on the border, and is incarcerating immigrants and immigrant children at a horrendous level.
Speaking in general terms, the policies that affect the border have always served to hinder migrants, particularly poor migrants, from being able to enter the US. In recent years, these policies and proposed policies stand to only raise suffering, death, and despair for migrants seeking refuge. After all, the US-Mexico border was created directly from the colonization of this land by Spanish, French, and British settlers who created an arbitrary national boundary that rendered people indigenous to this continent as "illegal". Now, decades later, this border is only becoming and more militarized as white supremacy, hyper-nationalism, and authoritarianism become more and more common place. Recently, a policy has taken affect that would allow immigrants to be denied entry/visas/asylum into this country if they plan on seeking basic survival necessities, such as food stamps. Other recent proposed policies would increase visa application costs by over 80%, massively tailoring the legal immigration process towards the wealthiest migrants, and forcing more and more migrants to face the incredibly dangerous and often fatal path of crossing the border undocumented.
Family separation and incarceration of children has become a common place practice at the border. In August, a person formerly employed as staff at a detention center that incarcerates migrant children in Chicago released a report on the horrendous policies, practices, and abuses that make up the immigration system and accurately called the incarceration of migrant children as "legalized kidnapping".
These policies benefit the wealthy and powerful classes within this country. While racist and anti-immigrant rhetoric attempts to blame immigrants for poverty within the US, the clear fault lies within this very system.