Any advice for an American visiting Europe (England, Netherlands, German, Switzerland and France) for the first time?

I decided to join a group tour this February because I have wanted to travel for a long time but haven’t gotten the opportunity yet?

If you’re a traveler or a European who had bad experiences with American tourists what advice would you give me?
Any advice for an American visiting Europe (England, Netherlands, German, Switzerland and France) for the first time?
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