For the example given, I would say that the average American would not misunderstand sweets or holiday. Sweets is used in AE, but not as a general rule. Holiday is used in AE, but not to mean a vacation. We might go on vacation during the holidays, for example.
We might, as a group, have alot more difficulty with other words like lorry, boot (trunk of the car) and other words that I can't think of because they would confuse me if I heard them.
With respect to the following list, I've noted which words I think might generally be more problematic:
Problem: B road (rural road)
Problem: bonnet (hood)
Problem: boot (trunk)
No problem: bumper (fender)
No problem: car park (parking lot)
Big problem: dual carriageway (divided highway)
Problem: estate car (station wagon)
Big problem: flyover (overpass)
Maybe a problem, depending on the context: gearbox (transmission)(gearbox might be confused with a tool box - the box where I store the gear)
Problem: juggernaut (18 wheeler)
Problem: lorry (truck)
No problem: motorway (freeway)
No problem: pavement (sidewalk)
NO problem: petrol (gasoline or gas)
Problem: saloon (sedan) (one should never drink and drive)
Not much of a problem: silencer (muffler) (although I generally think of a silencer with respect to a gun)
Problem: spanner (wrench) (although people who are handy with tools are familiar with the AE tool "spanner wrench" which is a particular kind of wrench)
Problem: ticking over (idling)
No problem: windscreen (windshield)http://en.wikipedia.org/wiki/American_and_Bri...