During his presidential campaign and throughout his presidency Donald Trump’s dealings with illegal immigration have sparked global controversy. The election of Donald Trump has thus insinuated a debate within the academic field of International Relations and a reoccurring concept within said debate is populism. This thesis includes itself into said debate through considering the empirical case study of the Trump administration’s securitization of illegal immigration. More specifically, it investigates how Trump’s securitizing speech acts fuel populism in the US which challenges discourses of open borders and subsequently affects US-Mexico relations. The thesis analyzes polls to captivate the US’ general population as an audience and applies discourse analysis on speeches held by Donald Trump to grasp how the Trump administration’s securitization of illegal immigration fueled populism in the US. It studies the negative effects of the securitization on US-Mexico relations by examining the reactions of Mexican presidents, members of the Mexican Foreign Relations Department and members of the Mexican senate. It is found that Trump’s rhetoric employed throughout the securitization of illegal immigration fueled authoritarian populism and xenophobic populism in the US which captivates the negative sentiments of the predominantly conservative Republican voters towards illegal immigration. The employed rhetoric subsequently challenged discourses of open borders. The effects of said challenges had negative implications on US-Mexico relations as the investigations of the reactions of the Mexican presidents, the members of the Mexican Foreign Relations Department and the members of the Mexican senate have shown.

"The purpose of this study was to show the position of Texas in the relations between the United States and Mexico from 1876 to 1910. With this thought in mind, the general problem has been to link the two countries through Texas. The Texas border relations between the United States and Mexico during this period were interesting because they showed the continued success of the efforts of the past years in building up better principles of settlement. " --leaf 129