I find the main difference between the US and Europe to be cluelessness and very different views about what good service might look like. My conclusion is that good service comes from management valuing good service and training (or firing) their staff accordingly.

The most common difference: restaurant wait staff aggressively removing plates as soon as or before you are done with them. While in Europe that obviously would be rushed and seen as overly aggressive and a hint that it's time to get the hell out to make space for other dinners. Super rude in Europe, considered attentive service in the US.

Striking experience: At an allegedly "five star" resort in the US, some wait staff being very loud and chummy with the guests to the point of disturbing the guests, and other guests, and neglecting other tables! Inconceivable in Europe - reserved for top management or owners. And failures to pay attention left and right - by all the staff everywhere. Clearly blameable on management defining the wrong parameters as objectives to their staff.

Tipping in the US is entirely hit or miss: some staff will remember past tipping, but only some. Some staff make a visible effort at service (before tipping), but only some. Etc.

But to be fair, there was a time when service in Paris got so bad and rude that the waiters corporation ran ad campaigns asking them to cut it out and do better. French service still has a bad reputation (of rudeness and scams). And there, it's very much NOT that waiters don't know what to do and not do. They know.

I would see working out "out of bread" with the neighbors as normal when the restaurant is not super busy, and "above and beyond" at rush hours. But then in France, running out of bread before very late in rush hours would be a clear management failure.