Nice try, pal - this involves a stay over the weekend - if you try to return on a Sunday (as, say, a working person in this country who gets on average 10 days of vacation per year would want to do) the price on US Air is $899 (quoted by Travelocity). The one stop flights are round $300-$400 and take about 6 hours - i.e. as much time and money is it takes to fly from Baltimore to London.
Now, Pittsburgh and Baltimore are fairly large cities, more than a half a million inhabitants - But if you consider medium size cities, say 100-250 inhabitants - which in Europe would have a wide variety of connections by train or bus - your only viable option here is driving. Do not believe me? Then try this: imagine you are a single working mom in Reading, a blue collar town in eastern PA trying to take her 2 kids to Ocean City, a popular working class sea resort in MD. Check what connection you can find for her and at what price and report it back to the class.
PS. What never ceases to amaze me about this country is that the people who get screwed up the most are also the most vocal supporters of the status quo and the most vocal opponents of any expansion of public programs that would benefit them. It seems that non-capitalist (i.e. non-utilitarian) attitudes of the working class are a necessary condition of the American brand of capitalism.
Wojtek