In the United States, there are a large number of organizations that offer immigration legal services to people who need advice on their procedures with the Citizenship and Immigration Service (USCIS) or other immigration situations.
In many situations for migrants in the United States, it is necessary and almost mandatory to have an immigration attorney who offers legal support for procedures before USCIS, or defense against detention or possible deportation. Fortunately, there are several national organizations that connect immigrants with attorneys who provide these types of legal services.
One of the largest organizations that provides this type of support to immigrants is the American Civil Liberties Union (ACLU), which since 1920 has been in charge of defending the civil rights of the population in the United States, regardless of their immigration status. This organization can make it easier for immigrants to find a lawyer. Learn more about the ACLU here: https://www.aclu.org/issues/immigrants-rights
Another highly relevant national organization is the American Immigration Lawyers Association (AILA), which through its network of volunteers offers legal services to immigrants and citizens in the United States. Services are usually free or low cost. In addition, AILA has an immigration lawyer search engine by geographical area, rates and other filters: https://ailalawyer.com/spanish/default.aspx
Immigration Advocates is another organization that makes it easier for people in need to find immigration lawyers. Through their network they invite non-profit organizations and Pro Bono lawyers to participate in their initiatives. Learn more: https://www.immigrationadvocates.org
On the other hand, the Department of Justice (DOJ), has a tool of Pro Bono lawyers that offer immigration legal services. Check out their tool and search by state: https://www.justice.gov/eoir/list-pro-bono-legal-service-providers