I have it directly from European CTO’s and founders that in Europe every country is its own market — not just rules and regulations, but culturally — significantly affecting consumer behavior.
In the US a launch is a launch into a market in excess of 300M potential customers, in EU you have to lather-rinse-repeat 27 times
There used to be more cross border banking until the Eurozone crisis exposed the structural flaw that under the regulations back then (and probably still currently) national regulators were responsible for bailing out headquartered banks, so you had small countries like Cyprus going belly-up because they had to bail out large cross-border banks.
VC markets are definitely not cross-border in practice.
Draghi's report claimed a big factor was the lack of a true financial union, which made it hard to mobilize and raise capital.