A.W.U.K.
True, but there are two comparisons to be made here. Pennsylvania is roughly the size of England, Pennsylvania is approximately 120,000 sq km while England is about 130,000 sq km. Likewise when comparing direct populations Philadelphia has a population of ~1.6 million compared to Birmingham's 1.06 million; and when comparing greater metropolitan areas, this ratio continues at ~5.8 for Philadelphia and ~3.7 for Birmingham. Almost uniformly, Philadelphia has a population 50% more massive. In downtown Philadelphia, blocks are approximately .125 miles or about .2 kilometers. The distance from the 30th street station to the 15th street station is about 2 miles or 3.21 kilometers. At a comfortable walking speed this is going to take about 25-30 minutes to walk.
I'll admit that I don't know much about the layout of England, but I am from a rather rural part of Pennsylvania. In "the country" (which refers to very rural areas) distances between houses are measured in tens of miles. There are areas where I could literally not see another human being, or even evidence of other humans, for days if I so chose.
The urban sprawl which, in my opinion, is something of an epidemic in America stems largely from the fact that the US simply has so much land available that we just don't think too much about space. This has led to most people literally needing to have a car to get to and from places within a reasonable amount of time. Around the larger metropolitan areas we do have a fair amount of public transportation, but it is nowhere as efficient as say Japanese or European public transport.
On the other hand, in two hours you can get to Baltimore, Washington D.C., and New York City by train.