Europeans have put too much trust in the US, getting less and less in return. NSA has no problem spying on our companies to undercut us in exports, the US justice system is used to bully European companies, etc. There is no way we will make the same mistakes with China !
The current EU was a brainstorm decades ago to have Europe consolidate to be a bulwark against the USA, so been done. The EU has its own legal system so mostly all done, now if there are any mistakes in those creations they can be easily rectified.
On the spying front, the US is in the minor leagues on that front, the rest of the world perfected spying long before the US and continue to do so with minimal percentage points of the billions the US is spending.
WWII showed us that the only persons the US could hide their nuclear program from was their own citizens...
The last trade deal that POTUS cancelled had the EU getting more than 50%, not much return for their efforts there either.
Usually for an international transaction of significance, you would use a major bank. The problem is that all these major banks deal with dollars. So there is a need to create a new major bank from scratch, basically.
Ok, I am confused here, if the problem is that all the major banks deal with dollars why do you need a new bank, is that not what the Euro was ultimately supposed to be, an alternative to the US Dollar? All the banks have to do is to trade in both and the EU can mandate that all EU trades are done in Euros and then it will spread, there is already a currency exchange where the Euro is traded against the other major currencies, including the US dollar.
All major banks are not US Banks nor all controlled by US interest, so the alternative already exist. Brexit is an opportunity for EU financial institutions.
I think the question is why are folks hedging their bet's, switch away from the US dollar and go, it may be rough or it may not be rough, but fear should not be used to hold back ambitions.