The major mistake that US executives make is not understanding enough about Europe as they try to attack the markets here. Learn about your markets, and you will be far better suited to meet their needs. Don't learn, and you will simply be guessing. As simple as this sounds, we have seen a number of US executives attempt to conquer Europe without spending the time to understand the very basics of the business environments here. They simply don't understand much about Europe at all.
Online companies have to work within the local culture.
Pure translations of US websites by themselves simply don't work. They failed to take into account the way in which Germans used the net. Users complained, and other portal sites were far more successful in Germany. US companies must be sure to go local, and not simply be the 'incoming foreign company' trying to capitalize on a less mature market. Sure, one can find content in other languages.