The European Commission has also proposed that the programming must be given "good visibility".
The move would affect US-based services including Netflix and Amazon Prime Video.
However, one expert suggested the new rules might not have as much impact as intended.
The call is part of a proposed update to the 28-nation bloc's Audiovisual Media Services directive.

Other measures include:
  • a requirement that video-sharing platforms including YouTube adopt "better" measures to protect minors from violent content and people of all ages from clips that act as an incitement to hatred
  • a call for the creation of new symbols or phrases that would warn viewers of potentially harmful video content - such as bad language, sex or drugs - that would be used across the EU by both broadcasters and internet-based platforms
  • the ability for TV broadcasters to have more flexibility as to when they show adverts   One industry watcher said that many of the online platforms already meet the proposed quota requirement because they carry so much BBC-made material.
    But even if the UK leaves the EU, and the BBC programmes no longer count, it would not necessarily mean lots of additional content from other countries being commissioned as a result.
    "This is driven by the core problem that the EU identified 40 years ago, that the Hollywood studios and other US producers dominate global box office and broadcasting because they have scale that cannot be achieved in a fragmented EU," commented Alice Enders from the media consultancy Enders Analysis.
    "It does send out an important signal to Netflix and others.
    "But let's face it, the online services could meet the 20% quota by loading up themselves with lots of rubbish French, Italian, Spanish and whatever content.
    "Or they could simply remove some of their lesser-watched non-EU material."
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