Given it's obvious similarity to much more modern rhetoric, which is more or less the impetus for the book itself, I thought it would be important to verify.
The quote in question comes directly via Hett's book:
Autarky was central to the Nazis’ political campaigns, and the theme of freeing Germany from its dependence on a hostile world clearly struck a chord with voters. The canny party propagandist Joseph Goebbels wrote in 1932 that a nation that couldn’t manage to get control over the “necessary space, natural forces and natural resources for its material life” would inevitably “fall into dependence on foreign countries and lose its freedom.” The outcome of the First World War and the nature of the postwar world had proven this clearly, he claimed. “Thus a thick wall around Germany?” he asked. “Certainly we want to build a wall, a protective wall.”
The citation Hett provides for this speech (and his publisher likely forced him to have a crummy endnotes system) is Volume 8, page 109 pages 7-8 of Ursachen und Folgen. Vom deutschen Zusammenbruch 1918 und 1945 bis zur staatlichen Neuordnung Deutschlands in der Gegenwart. Eine Urkunden und Dokumentensammlung zur Zeitgeschichte edited by Herbert Michaelis, et al. This is a fairly standard reference work used by scholars for primary source speeches and writings by figures between 1918 and 1945.
Someone who has access to a copy of this particular volume of Ursachen und Folgen might be able to double-check Hett's translation here, but this type of rhetoric was not inconsistent with Goebbels's speeches. The phrase Schutzwall (protective wall) was not an uncommon one for Goebbels and other Germans of this era. Goebbels used it in his 1943 Sportpalast speech in which he described the Wehrmacht as a barrier against the East. Hitler's speeches often used fortress metaphors to describe Germany's situation as a nation allegedly encircled and under siege. It was also not uncommon for German nationalist leaders to decry the flood of refugees and so-called Sachsenganger, seasonal agricultural workers from Poland. Even though the use of migrant workers had declined under Weimar compared to the Kaiserreich, border controls and migrant labor were hot button issues in Weimar politics. Of course, some these walls were metaphorical, but the Third Reich did begin a rather intensive construction of fortifications on its borders such as the Siegfried Line and the less well-known Ostwall.
So Hett's translation might be a bit on the nose given 2018 American politics, but it is not an implausible parallel.