I've driven down some god-forsaken little country road on the wrong side of the street in Ireland to look over the edge and see the Cliffs of Mohar south of Galway. But -- hell -- you can drive along, down and back up cliffs that are five times as breathtaking if you head up or down the Pacific Coast Highway from San Francisco in either direction.
I've paid a few francs or lira and climbed to the top of Sacre Couer and St. Peter's and both are worth the trip for their religous significance as well as their views of the ancient cities. But they are nothing compared to standing facing southeast from the Sun Temple on Mesa Verde in Southwest Colorado or standing on Byron's Ledge (no known relation) looking into an active Kilauea on Hawaii. And those are views that are free if you have the senior pass from the National Park Service.
I've paid to take the Hovercraft from Calais to Dover and my employer has paid for me to take a water taxi from a hotel in Venice to the Marco Polo airport on the mainland, bypassing all the tourists working their way from gondola to water bus to trolley to real bus... dropping a few euros at each transfer. It was more impressive to head down route 87 from Louisiana and take the ferry across the mouth of Galveston Bay... to Galveston Island... just missing supertankers heading in both directions... for free.
(I'm not sure if it is still free and the time I did it, 87 had been cut somewhere between the La. state line and Port Bolivar by a hurricane, forcing you to detour inland for an hour or so. Our GPS didn't seem to know that but that's what driving around the U.S. is all about. Also I don't think the woman I talked to in Guffey understood my Boston accent... and vice versa. But if I heard her right, the road was washed out in 1987 and isn't likely to ever be replaced. Another guy in that little Texas Gulf town says about once a year a big semi barrels right through that "Road Ends" sign and scares the hell out of a bunch of duck hunters.)
I like Europe. But you can't beat touring the United States when it comes to getting your money's worth.