I've worked with a few americans on a few decent sized projects, 3M and GEAES.
In a work environment they tended to be a little humourless and a little insecure. It would be silly to judge a country on 6 months of working with 20 or 30 people, but it was quite a surprise.
It was also quite a surprise that they regularly did the old B&Q trick and would mix measurements, telling me something was, say, 6'2" by 575mm. That does my crust in.
By contrast, the Germans were bang up to stereotype in being uber efficient at work - but with buckets of irony and sarcasm thrown in, plus a desire to drink every night after work.