Imagine if US President Donald Trump could flip a switch and turn off Europe's internet.

It may sound far-fetched, crazy even. But it's a scenario that has been seriously discussed in tech industry and policy circles in recent months, as tensions with Washington have escalated, and concerns about the EU's reliance on American technology have come to the fore.

At the root of these concerns is the fact just three US giants - Google, Microsoft and Amazon - provide 70% of Europe's cloud-computing infrastructure, the scaffolding on which many online services depend.

And some question whether an unpredictable US leader would weaponise the situation if relations seriously deteriorated - for example, by ordering those companies to turn off their services in Europe.

"Critical data would become inaccessible, websites would go dark, and essential state services like hospital IT systems would be thrown into chaos," says Robin Berjon, a digital governance specialist who advises EU policymakers.

He believes that concerns over a so called US "kill switch" should be taken seriously. "It's hard to say how much trouble we would be in."

Microsoft, Google and Amazon all say they offer "sovereign" cloud computing solutions that safeguard EU clients' data, and would prevent such a scenario ever occurring. The BBC has contacted the US Treasury department for comment.

In truth, there have always been concerns about the lack of "digital sovereignty" in Europe, where US firms not only dominate the cloud-computing market, but also hardware, satellite internet and now artificial intelligence.

Even the region's main mobile operating systems - Apple and Android - and payment networks - Mastercard and Visa - are American.

Those fears became urgent in May when it emerged that Karim Khan, the top prosecutor at the Netherlands-based International Criminal Court (ICC), had lost access to his Microsoft Outlook email account after being sanctioned by the White House.

The ICC has issued arrest warrants for top Israeli officials, including Prime Minister Benjamin Netanyahu, over their roles in the Israel-Gaza war - something Mr Trump called "

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