Plus there was always more of a sense of community
Yes, of course. It was sort of imposed on Brits coz there were many of them on a relatively limited area. They had to develop that sense in order to prevent tensions, leading to animosities or even civil wars.
While Poland had more territory and people lived far from each other - that influenced the character of Poles and shaped today`s individualism.
The US is a bit different isn't it? I mean those completely open plan gardens with no obvious boundaries at all
No, in Am suburbs those open plan gardens aren`t so big. Most gardens the size I am thinking about are usually fenced in Poland. Even bigger ones.