This petulant, foot-stomping demand has been prevalent among the nativists for a long long time in the UK and in the USA.
Of course, the fact that many of the most aggressive complainers clearly have no effing clue about how write or spell English does rather tend to undermine their credibility.
Nonetheless, the demand still keeps being made.
When I look at history, I find the obsessive demands of nationalists from English-speaking countries “speak English” to be highly amusing.
Languages developed and evolved organically over many thousands of years when various groups and tribes of people developed common means of communication. Languages were carried over many thousands of miles by migrations of groups of humans, but those languages did not remain static and continued to evolve.
English is one of the ultimate “mongrel” languages, nominally a Germanic language, but heavily influenced by French, Celtic and old English langugages.
The rise of the modern nation-state, with rigid borders seen as permanent by its residents, is a relatively recent development. With the rigid borders has come a rigid idea that the majority language within the country should always remain the same.
Within those nation-states, however, languages continue to evolve. I am a poor French speaker, but I can tell from reading pages in French on the internet that modern idiomatic French is nothing like the French I was taught in school. Within France, there is a serious-sounding body, the Academie Francaise, that considers itself to be the arbiter of what is acceptable French. The problem is that the Acadamie is attempting to mandate features of a language that is evolving around it. One example from a while back was it’s insistence that French should not contain the loan word “weekend”. The Academie insisted that “fin de semaine” was the only acceptable phrase. Most of the French nodded, and then went back to saying “un excellent weekend” to their friends on Fridays. You can’t mandate language like that. It’s a lot more fluid than many people realize.
The cry of ‘speak English!” is understandable, but what the people doing the crying don’t realize is that by 2100, American English will have evolved to the point where they may not even recognize it. As the percentage of Hispanic people increases, loanwords from Spanish and Meso-American languages will form a larger proportion of the vocabulary, and sentence structures may change more towards a Spanish form of construction. The pseudo-language known tongue-in-cheek as Spanglish may become the lingua franca in the USA.
The “speak English” demand is really a not very well hidden statement of “keep things just as they are. NOW”.