This is how the US has the Europimps by the short and curlies (to say nothing of trade finance and other related matters):

To finance or raise money for its business (to build a new plant or build new ships)  a company issues debt.  It engages advisers, valuers and an investment bank to sell its corporate debt to investors. To reduce its cost of borrowing it needs to tap the most liquid and biggest debt markets such as those of the US.

To sell to the investors in the US, the issuer is required to include restrictive covenants in the bond.  In other words it has to adhere by certain rules otherwise it will be in default.  One of the main restrictive covenants requires the issuer's strict adherence to US as well as local laws, including such measures as US sanctions and FCPA (Foreign Corrupt Practices Act) often spelled out in no uncertain terms in the bond documents.

In today's interconnected world the Europimp governments cannot bypass the US to save the Republic of Murder and Mayhem. And it is not simply a matter of avoiding USD payments. 

Smart sanctions work if it was not for Appeasers in Chief looking for legacies (or reality TV stars looking for quick victories - the jury is still out on Trump and his backtracking on ZTE does not inspire confidence).