While marriage is increasingly seen as a completely optional "folkloric tradition" in Europe, it is still quite important in the USA (probably because religion is also more important there). Statistically Americans marry much more than Europeans, but also divorce more. Gay marriage, now legal in several EU countries and hardly an issue for debate in Europe (because of the little importance of marriage in Europe nowadays), is still vehemently opposed by a big part of the US population.
Wedding ceremonies are also much more important and formal in the USA. In most of Europe it is limited to an informal family gathering (usually at the bride or groom's parental home). Marriage traditions do vary considerably between European countries, and even more between families. But in average it is certainly less important than in the States (or in Asian countries for that matter).
Furthermore, there are some strong nationwide American traditions regarding wedding ceremonies, like bringing "something old, something new, something borrowed, and something blue". There is obviously no equivalent thing at a European level, and most often not even at a national or regional level.
In fact, even the way of dating tends to follow so well-defined rules in the USA. For instance, there are widely followed conventions about sleeping on the 3rd date. Men know they shouldn't expect to see a woman again if she insists to split the bill ("check" in AmE) at the end of their first date. The way of proposing, or buying an expensive ring are more important for Americans too. In Europe, the way of doing things is more informal and spontaneous, and can varies a lot from one region to another, and even on a person to person basis. Sometimes, that makes Europeans envious of how easy and clear things look in the USA in comparison. The drawback is that it seems too stereotypical, especially if you don't like the conventions.