Big one page article in today's Journal about "Europe is opening to US tourists." It's behind a paywall, I'll excerpt what I can.
One big piece of advice "If you are waiting to book until you are 100% sure you can actually enter a particular country or countries, be ready to pounce. Ticket prices and demand tend to shoot up at the slightest policy change."
To balance that, Points Guy had a long list yesterday of the status of every country in Europe. Even if they aren't shut down to Americans, which most of them are, the US State Dept. is disadvising travel to just about everywhere. As of now. YMMV.
WSJ says we are on England's amber list, which means you need a COVID test before flying AND are subject to tests and a 10-day quarantine upon arrival. However Scotland, Wales and Northern Ireland may have different rules.
They advise that most French sights are outside which is good, but almost everything else requires advance reservations.
Cinque Terre and the Amalfi Coast are already filling up with walkers, and again most Italian sites require reservations.