Original here . Edited for style, not content.
This is one of the arguments the right uses to attack immigration from Mexico.
Although until fairly recently Mexico was a one party state , I don't think right wingers base their opinions on an understanding of Mexican history. Often when dictatorships in Central and South America are brought up there are either covert or overt suggestions that they’re there because Latinos don't understand democracy. Commentators conveniently overlook the influence of U.S. foreign policy.
What's interesting is that the idea that immigrants "don't understand democracy", and the implication that mass immigration will turn the U.S. into a third world dictatorship, isn't new. It was used in a successful campaign to keep immigrants out from Southern and Eastern Europe.at the beginning of the 20th century.
The nativists argued that Southern Europeans, principally Italians, came from a state without democracy, which wasn't true post-Italian unification, that they were racially inferior, as well as Catholic, and so naturally under the authoritarian sway of the pope.
The argument against Eastern Europeans, was that they were completely outside of history, unlike Italians, who were at least bearers of representative institutions in the Renaissance and in Roman times. They also spoke languages that didn't even resemble English and were either Catholic or Jewish.
In fact, although I only briefly looked at it, there was pre-World War I book called "The Slavic Invasion", a classic 'They're taking our jobs' book, that dealt with the threat of mine workers from Slavic countries.
The Immigration Act of 1924 was heartbreaking in its simplicity. Besides outlawing immigration from Asian countries, it instituted a 2% rule, pegging the number of immigrants from a country per year was to 2% of the amount of population claiming that descent in 1890, before the influx of Southern and Eastern European immigrants. Later, the index year was changed to 1920.
Because the Irish and Germans formed a large percentage of the U.S. population in 1890, these countries got preferential treatment, even though immigration from Germany and Ireland had slackened off. Scandinavian immigration got a boost, and, perversely, a high amount of immigrants were allowed in from Africa, although few took advantage of it.
Here's an example from Wiki's article on the act:
"As an example of its effect, in the ten years following 1900 about 200,000 Italians immigrated every year. With the imposition of the 1924 quota, only 4,000 per year were allowed. At the same time, the annual quota for Germany was over 57,000. 86% of the 165,000 permitted entries were from the British Isles, France, Germany, and other Northern European countries."
Here is a chart from George Mason University showing the quotas.
An example: 3,954 were allowed in from France per year, although French immigration to the United States was miniscule, while 3,845 Italians were let in every year, although 200,000 had been coming in yearly since 1900.
It's funny how soon people forget the past, and how some people whose ancestors were abused, like Italians, who are still on the bottom of the white ethnic U.S. hierarchy, form part of the vanguard against immigration from Mexico. Such as people named "Tancredo". My intuition is that Tancredo isn't an English name you can find in British census records going back centuries. If the Tancredos had tried to come over from Italy after 1924 there's a significant chance they'd have been refused.