The Catholic Church in the United States is an immigrant Church with a long history of embracing diverse newcomers and providing assistance and pastoral care to immigrants, migrants, refugees, and people on the move. Our Church has responded to Christ’s call for us to “welcome the stranger among us,” for in this encounter with the immigrant, the migrant, and the refugee in our midst, we encounter Christ. The Church does not make a political statement and Catholic Catechism does not oppose border security:
The Catholic Catechism instructs the faithful that good government has two duties, both of which must be carried out and neither of which can be ignored. The first duty is to welcome the foreigner out of charity and respect for the human person. Persons have the right to immigrate and thus government must accommodate this right to the greatest extent possible, especially financially blessed nations: "The more prosperous nations are obliged, to the extent they are able, to welcome the foreigner in search of the security and the means of livelihood which he cannot find in his country of origin. Public authorities should see to it that the natural right is respected that places a guest under the protection of those who receive him." Catholic Catechism, 2241.
The second duty is to secure one’s border and enforce the law for the sake of the common good. Sovereign nations have the right to enforce their laws and all persons must respect the legitimate exercise of this right: "Political authorities, for the sake of the common good for which they are responsible may make the exercise of the right to immigrate subject to various juridical conditions, especially with regard to the immigrants' duties toward their country of adoption. Immigrants are obliged to respect with gratitude the material and spiritual heritage of the country that receives them, to obey its laws and to assist in carrying civic burdens." Catholic Catechism, 2241.
To learn more about the Church’s teaching on immigration, we encourage you to visit the US Conference of Catholic Bishops’ website at http://www.usccb.org/issues-and-action/human-life-and-dignity/immigration/index.cfm.
For a Catholic perspective on the larger issue of Church and State, here is a recent article: https://www.faithandculture.com/home/2019/1/2/church-and-state