“It will be more difficult. And there will need to be much more effort by the UK to have a true influence on the world.”
The former ambassador said the future of world politics will be primed around a new “Cold War” between China and the US which is likely to see Britain fall to one side.
She commented: “There is a triangular (China-EU-US) relationship and it is harder for the United Kingdom to play a role.”
Britain voted to leave the EU in June 2016 by 52 percent of the vote to 48 percent.
However the exit was delayed a number of times and only finally took place in January 2020.
Until the end of December 2020 Britain remained in a Brexit transition period, during which it continued to pay into the EU budget and implement many laws made in Brussels.
Ms Bermann also claimed Britain would become less useful to the US post-Brexit, with the “special relationship” being “above all special for the British”.
Ms Bermann said: “The British vaccination campaign is better than the European one. Bravo for that.”
However she added: “This is not totally due to Brexit as the vaccine orders were made while the UK was still subject to European rules.”
Had Britain remained an EU member it would have come under strong pressure to join the bloc’s centralised vaccine purchase scheme.
France has only vaccinated just over five percent of its population versus 32 percent for the UK.
The EU is also lagging behind other advanced economies like the United States and Israel.
French president Emmanuel Macron caused outrage earlier this year by branding the Oxford-AstraZeneca vaccine “quasi-ineffective” for those aged over 65.
Data has since confirmed the jab is extremely effective for all age groups.
After initially restricting the Oxford vaccine to the under-65s France has since reversed its policy.
On Saturday Brexit architect Nigel Farage announced he is stepping down as leader of the Reform Party and from active political involvement.
Appearing on the Daily Telegraph’s Choppers Politics podcast he said: “There is no going back – Brexit is done. That won’t be reversed. I know I’ve come back once or twice when people thought I’d gone, but this is it. It’s done. It’s over.”