My American shoot-from-the-hip response to this would be to consider the road differences. Most American roads, interstate, state highways, and main city throughfares, are able to accommodate large vehicles quite easily. This is not the case in EU cities built for smaller traffic volumes. Many American vehicles are built to spec for these roads, and the difference between driving dad's F-250 and a garbage truck becomes less significant. Tractor trailers, farm vehicles, and heavy machinery are classed differently. But a petrol-driven bus or heavy-load truck is not.
There are a few places in Europe that you wouldn't be able to get to - the centres of some small villages, for example, or some smaller residential streets - but they're a definite minority. Don't forget we have buses and delivery trucks here, too!
Oh yes, certainly -- It's not a matter of the roads being incapable of supporting large vehicles period, but simply that many of those roads are not as accommodating to large vehicles as those of American cities. Thus it would require much more operator care to successfully navigate with those large vehicles.
