Elegua, integration isn’t the issue here. The fact is that the United Kingdom has at the moment an influx of migrant workers - like the US at present - which was Ralpy’s point.
Also, having just had a look at various population pyramids indicating statistics for both the UK and the US, it shows both countries have a current decline of new births except for the last 3 - 5 years, which shows that the number of newborns for both countries is now increasing (as you would have thought in the UK due to all those single, teenage pregnant girls hanging around the shopping centre every day).
Both the UK and US population pyramids look pretty much the same (except our pyramid looks better and is more well presented 
)
