http://www.rome2rio.com/s/Venice/Interlaken-Switzerland
As for renting cars, some countries won't recognize your license as a valid driver's license (I know Spain doesn't) unless you get an IDP (International Driving Permit). Plus, you need to learn the road rules for each country you drive in so you don't ruin your trip by getting in an accident.
To be honest, I don't recommend renting as the road conditions and driving quality vary greatly from country to country. For example, there are no multi-road lanes in the former Yugoslavia. At max, you get one lane going each way which leads to madness since drivers there don't give a **** about what's in front of them when overtaking a car around a sharp bend at 100 km/hour. You should see what crossing the border between those countries is like. I guarantee that you'll appreciate riding a bus then since they skip every car in the line.
On top of that, I feel you get to enjoy a country more when you walk or cycle through it. With driving in a city by car, you're only focusing on going from one place to another. For example, Amsterdam has more bicycles than people (over a million bikes for 800,000 people). Nearly half of the city commutes to work by bike. It's extremely bike friendly. There are also a lot of pedestrian-only areas that cars simply can't access. Add on the nightmare that is parking in a busy European city and you'll either need to pay out the ass to park at a parking garage or miracle your way to a spot on the street.
The main benefit of car rental comes when traveling to remote areas that are either inaccessible or poorly accessible by public transport. Aside from some parts of Eastern Europe and the Balkans, that's a non-issue. Any area regularly visited by tourists has the public transport necessary to accommodate it. The only other benefit is if you need to travel in the middle of the night as most cities do not have around the clock public transport like NYC does. So if it is necessary for you to travel at 2 or 3 AM and prefer not to use a taxi, then a car is useful.
It's a matter of personal choice. I choose not to use cars and I don't feel restricted with public transport, cycling, or walking.