Many Americans are a bit uncomfortable driving in Europe, especially when signs are in a language they don't understand. This discomfort increases in major cities where traffic on Europe's smaller roads can be heavier and more confusing than in large American cities. Parking can be a serious problem in European cities, often solved only by long walks to and considerable expense at overcrowded parking garages. Parking tickets incurred while you rent a vehicle will be charged to your credit card if not settled with the local police prior to your return to your home. This is frequently omitted from auto rental advertising, or buried in fine print.
Insurance is recommended, and in some countries required.
Credit card companies offering auto rental coverage do not always provide complete coverage, may not cover your entire rental period or exclude some countries completely. Some car rental companies will not accept such credit card coverage. To a greater extent than driving, train travel costs depend on how and where you travel. Combine the best features of long distance rail with the flexibility of auto rental.