I agree that the majority of RVs in the world are found in the USA - but so are the majority of the worlds GA aircraft!
As for the Lycoming/Rotax debate there's enough Lycomings around which work perfectly well and reliably to TBO and beyond. They may not be the most efficient but they don't need radiators, coolant, gear boxes etc to complicate things.
Build an RV, fit a Lycoming in it and fly the a*se off it and you'll see why they are hard to beat as an all round excellent flying machine.
How many Europ/Ban-bi owner/builders have gone on to build another? How many and in how many countries do they operate compared with RVs?
If you don't believe me just go and blag a ride in an RV and try and stop grinning afterwards....
PS The V220 Bombardier engines are very pretty and I'd love one in the nose of the RV but I fear they might be a tad more expensive than a new Lycoming. Still, could be worse, people might start extolling the virtues of diesels........