Help for the US driver hiring a car in Europe
Renting a car when in Europe is an excellent way to get around. Distances between the majority of European countries are relatively small for American drivers, who are used to driving many miles to get between states. It is rarely worth flying between countries unless you're on a very strict time schedule, or are literally going from one side of Europe to the other.
There are of course some considerations. You will want to read up on traffic laws in the countries that you will be visiting, as laws definitely vary by country.
Drink driving laws in particular are very different from American laws, with a lower tolerance for alcohol in your blood stream, and some countries having zero tolerance, meaning you can't have even one drink.
Once you're confident that you can drive legally, you will want to decide on what kind of car you should hire. Your choice of car really depends on what kind of driving you're going to be doing...
The best choice for city driving is a sub compact. Many European cities have extremely narrow roads, and double parking along roads is common. You will frequently be forced to squeeze your car into tight spaces, not just parking spaces but road space as well. And there aren't many places where you'll have room to turn around an SUV when you inevitably get lost.
If you are only two people, you might want to consider renting a Smart car. These cars are ultra small, narrow, and specifically designed for easy city driving and parking.
There are beautiful mountain ranges in Europe, and whether you're interested in skiing, or just in seeing the scenery, an SUV is probably your best bet. A compact SUV would be the ideal choice, as mountain roads can get quite narrow, but since they are also steep you'll need an engine with a bit of power to get you around.
Don't forget that in the spring and fall it's very likely that there will be snow on mountain roads, even if the weather further down is beautiful. Tell your car hire company where you are planning on travelling so that they can ensure you have the correct tires. Many European countries have roads that are closed to cars without winter tires, and you can be stopped and fined if you don't have the appropriate tires on your car.
Of course the term long distance is pretty relative when you're talking about driving in Europe. But still, it does take quite a while to drive from the north of France to the south of Spain, for example. Your best choice kind of depends on your route.
If you plan on travelling long distance through Germany, for example, you might want to consider a powerful full size car, as it will be comfortable and most of the German Autobahn has no speed limit.
Driving in France and Spain on the other hand can be a little more troublesome. In particular Spanish highways can be narrower than you're used to. A compact family car should make sure that you're comfortable, but still able to fit into narrow highway lanes and get where you need to go pretty fast.
Avoid sports cars if at all possible, they look tempting, but safety concerns are paramount when driving in unfamiliar countries. Remember that European roads, even highways, will probably be much narrower than you're used to, and the speed limits higher than you're used to.
Particularly in the south of Europe, driving standards are not particularly high, and roads can be dangerous. Having a safe car is especially important under these conditions.