But yes, Amtrak does go very slow, at least the one time I used it it did :)
US: http://jaymans.files.wordpress.com/2012/09/71789-050-459169a...
EU: http://education.randmcnally.com/images/edpub/Europe_Populat... (note the very different colour schemes).
Bad tracks and diesel locomotives are more likely to be the culprit here.
As an example, the Amtrak train that runs between Washington DC and Boston (serving NYC along the way, and continuing on to Norfolk, VA) stops not only at DC's main train station, but also at New Carrollton, MD and Alexandria, VA, which are not only quite close to DC, but actually on the DC Metro system, making these stops almost completely redundant.
I count no less than thirty two stops between Boston and DC. The trip is about 9.5 hours long, so that's an average of one stop every 18 minutes.
The NYC->Chicago trip isn't quite as bad, but still has 19 stops in between. Along the way, it stops in such bustling metropolises as Elkhart, IN (population 51,152) and Sandusky, OH (population 25,493).
The typical Northeast Regional between D.C. and NYC is: New York City, Newark, Metropark, Trenton, Philadelphia, Wilmington, Baltimore, BWI, New Carrolton, D.C. That's 8 intermediate stops over 3.5 hours, or one per 26 minutes. The Acela Express doesn't stop at Metropark, Trenton, BWI, or New Carrolton.
Why does even the Acela pass through Wilmington? The city only has 70,000 people, but is also a hub of corporate law firms and credit card companies. Wilmington boards about 800k passengers per yer, versus Baltimore's 1m, despite the latter being about 10x as big.