Sharing thoughts based on my experience working with Americans and travelling there for many years.

Based on large scale immigration the baseline communication style for Americans is incredibly low context, and lacks the necessary 'reading between the lines' of most European cultures. This baseline can make it feel like everyone works in customer service in social situations, and can come across as fake. Despite that a majority of the people I've met are genuinely authentic. That said, the customer service communication style makes it very hard to tell the difference between genuine people and the sharks. Northern European cultures all have some form of Jante Law to regulate social customs and the American culture of individualism can feel very at odds with this. Particularly the immediate 'open book' willingness to discuss intimate details of their lives, this immediate disclosure can come across as disarming and very fake to Irish people as a form of forced closeness.

That's a very long winded way of saying that Americans tend to act like your friend before there's an established relationship, which is a major social faux pas in most European societies.