Houses in the UK compared to the US and continent are a lot smaller in general. (Cos we have to squeeze 62 million of us into a tiny country!)
In comparison to other European Nations, the population density of the UK is roughly equivalent to Italy, Germany, the Netherlands and Belgium (ranking roughly 50th out of 220ish nations worldwide). Most Northeastern States of the US have population densities greater than the UK.
Size comparisons to other European Nations places the UK above Romania, Belarus, Greece, Bulgaria, Serbia and Montenegro, Hungary, Portugal, Austria, Czech Republic, Ireland, Lithuania, Latvia, Croatia, Bosnia and Herzegovina, Slovakia, Estonia, Denmark, Netherlands, Switzerland, Belgium, Slovenia and Luxembourg (discounting micro sates).