Eu countries are accepting visitors on production of the EU digital COVID pass , or typically 72 hour validity PCR tests. ( which can awkward if sailing )
The
current issue is there no general agreement on how to handle US vaccine proofs. So there are reports of people running into difficulty.
All the countries you mention are normally “ open “ to US visitors subject to COVID restrictions
Remember as US citizens you will need to enter the Schengen area through a port of entry to have your immigration status verified.
The situation is unfortunately very fluid especially when arriving via a yacht. But the countries mentioned are not closed to international yachts at present. ( we shall see as
delta progresses )