Bob Wakabayashi translated Aizawa Seishisai's Shinron (New Theses, 1825) in Anti-Foreignism and Western Learning in Early Modern Japan.

Aizawa is clearly worried about Western imperialism and hated the West, but he saw it more as Christendom overtaking the world. It's not exactly seen as an economic conquest just yet. (So in his mind it was a cultural contest between Christendom vs Confucian Japan.)

From Japan's perspective in the early 1800s it wasn't just Britain and France that was threatening, it was really Russia that was threatening. What united all three was Christianity (Protestant, Catholic, and Orthodox), so it was natural for Aizawa to think in terms of religion. He seriously thought that Christianity first converted local people and then the converted Christians acted as a fifth column for the Europeans to take over. This New Theses became very popular in Japan and led to the growth of xenophobia among the samurai.

Interestingly after the Opium War (1839-1842), shogunal officials recognized that the Europeans were not driven by religion but by profit above all else. Unfortunately as far as I know this is not available in English books, but it's recorded in the Bakumatsu Gaikoku Kankei Monjo.

https://www.hi.u-tokyo.ac.jp/english/publication/komonjo-e.html

After the 1850s, as more Japanese began to leave Japan and witness Western colonial rule in Shanghai, Singapore, India, part of Middle East, leaders like Takasugi Shinsaku became very worried that Japan might be next. The Iwakura mission toured not just America and Europe, they visited the rest of the world as well. They have to be blind to be oblivious to all this. Kume Kunitake has left a great record in the Bei-O kairan jikki (parts of which has been translated as Japan Rising: The Iwakura Embassy to the USA and Europe).

This fear was one of the great drivers of change in Meiji Japan.