I understand your frustration and have experienced intolerable waits in European restaurants much more so than in the US. However, it does occur here in the US as well.

In my mind, the ideal situation is for the server to come to the table regularly and after dessert has been served or declined, ask if there would be anything else or would I like the check now. After the check has been presented, I am as obvious as possible when I am ready to pay. I usually stand the portfolio (I'm stuggling for the right word to describe the thing the bill comes in) on end with the credit card sticking up out of the top.

The opposite side of the coin is being rushed. This is equally frustrating. Do not ask the table about dessert as long as one diner is still obviously working on the entree. Do not bring the entrees while one or more diners are working on a salad. Don't put the check on the table without asking about dessert or another round of drinks. Etc.