The UK’s GDP per capita trajectory diverged around the end of the Great Recession. That was before the Brexit vote (2016) and long before the actual Brexit (2020). France and Italy have been stuck in more or less the same doldrums since the same time: https://datacommons.org/place/country/FRA?utm_medium=explore...
It would be somewhat unusual if they didn't all look similarish given the level of trade between them.
The UK government predicted a 2% reduction in growth over 15 years with a soft brexit compared to what it would have been otherwise, but seeing it on a graph may be difficult given those countries were also hurt by Brexit.
I'm not disagreeing with your main point (by a host of metrics, the UK and EU have stagnated economically compared to the US since the end of the great recession), but I also don't think GDP per capita is the best metric to use here given widening levels of inequality. Median income levels taking into account government transfers are much more informative in my opinion.
As a fairly regular visitor (for work), what particular doldrums are you referencing?
Admittedly, the loss of the US market will be a big blow for exports, but the anti-US (Trump) feelings strongly would put up with a financial hit rather than dealing with Mr. Loopy.
And Tesla's are becoming very unpopular...and unsellable.
I'm as anti-Brexit as they come, but it didn't change the UK's direction much. It's still the 2nd richest European state (with the 1st declining fast), the 3rd largest tech ecosystem worldwide, one of the premier military powers. Brexit wasn't great, or even good, but it's not disastrous.
That’s because Europe overall is declining fast. However the rest of the world is rising fast and the next ten years should be interesting from this alone.