The penny about the US’s worldview dropped for me when I recently interviewed a highly educated, accomplished, politically and racially literate American. I mentioned something about the British empire and he looked at me blankly. “What is that exactly?” he asked.

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This isn’t a criticism of individual Americans; many British people themselves don’t know their own imperial history. It’s a feature of what is taught in schools and purveyed in the media, which is myopic.

But news about the 2020 Oscars this week did bring that particular exchange back to mind. The Academy was considering a Nigerian movie called Lionheart in its best international feature film category. I watched Lionheart when it came out last year, partly because of the novelty of seeing a movie from Nigeria’s burgeoning Nollywood film industry on Netflix.

Directed by and starring the Nollywood titan Genevieve Nnaji, it is a captivating look at family, class, sexism, politics and the texture of life in the Niger delta. It’s both very Nigerian and very relatable for audiences who know nothing about Nigeria. It’s incredible that Nigeria has never had an Oscars submission before, but this is a good choice for its first. Yet Lionheart has just been disqualified because there is too much English in it.

In fact, Lionheart does feature the Igbo language, which millions of people in eastern Nigeria speak. But the film reflects the way many Nigerians – as former imperial British subjects – speak in real life. As in most of anglophone west Africa, education, politics and formal economic activity is conducted in English, which people interchange with the dozens – in Nigeria’s case, hundreds – of African languages that they also speak. This is the legacy of empire. And this legacy of empire, even though they were once part of it, is what some American institutions don’t seem able to comprehend.

So the American Academy expects films competing in its “international feature film” category to emphatically not be in English. Its rules are very clear on the matter, stating that “an international film is defined as a feature-length motion picture (defined as over 40 minutes) produced outside the United States of America with a predominantly non-English dialogue track”.

But these rules have nonsensical implications. For example, the Algerian film Papicha, which is a favourite in the category, features a good deal of French – the language Algeria inherited from its colonisers. The message seems to be that as long as your imperial power spoke what Americans regard as a “foreign” language – in other words, anything but English – you can speak it and remain authentic. But if you share an imperial past with the US to the extent that English is your nation’s lingua franca as a result, then it is somehow less authentic to speak it.

It’s ironic on so many levels. One of the reasons it’s taken African countries so long to build modern film industries is that Britain – while also imposing the use of English – made a concerted effort to suppress them. The British saw the power of cinema as a crucial propaganda tool for their own purposes, and consequently emphasised the importance of censoring anything that might have given Africans a sense of pride in their own history and heritage.

Now this same colonial history is being used to shut down Africans’ against-the-odds achievements in doing just that.

The takeaway message from the Oscars is that Africans from parts of the continent that were colonised by Britain must perform in an African language – regardless of how they speak naturally – in order to placate American ideas about what authentic African-ness is. It’s a new kind of reverse colonialism that is breathtaking from an awards ceremony that is still supposed to be learning the lessons from #OscarsSoWhite.

The American film establishment is clearly struggling to grasp the basic idea that there are Africans who speak English. Viewers get this: Nollywood box office revenues increased by 36% last year. Streaming services get this: Netflix and China’s StarTimes are among those racing to benefit from the incredible talent and energy coming out of African film industries in Nigeria and elsewhere. And international investors get this, like the French pay TV group Canal+ which has just acquired a major Nigerian studio. But the Oscars doesn’t get it. Again.

• Afua Hirsch is a Guardian columnist