It's supprising as that's from an xmas light company and I don't really see any huge differences between European and US setups to be honest other than the supply voltage and frequency and some countries may have slightly stricter guidelines on outdoor electrical installations but generally these wouldn't have any bearing on the actual lights.

E.g. in Ireland I can't see why using 110V centre tapped supply ~55V on each leg would be any problem with US lights. You would just use yellow CEE-17 plugs and sockets and an appropriately rated xformer. They would actually be much safer in that setup than they would be in the USA where it would be 115V to ground and possibly without all of the safety features that a site xformer provides here. In fact using that setup is one way of complying with the outdoor electrical safety requirments without resorting to 12/24V sets.

As for mains voltages in use outdoors here we do have tougher requirements than the USA but also tougher than most of the rest of Europe too. If you were to use 220V (230V) lights here you need to take a few steps to ensure they don't cause shocks.

1) The fittings have to be enclosed / fully weatherproof e.g. you need to use lanterns or specially designed fittings
2) Where 220V lighting is used it should be out of touch reach of the general public.
3) All fittings must be outdoor rated.. i.e. blue CEE-17 sockets/plugs and proper outdoor junction boxes.
4) It absolutely must be RCD protected and circuits need to have appropriately rated overcurrent protection e.g. neozed fuses / MCB. Ring circuits are also not acceptable outdoors other than where an outdoor circuit is connected into an interior ring as a 13 or 16A fused spur.

However, you'll find that the vast majority of older iinstallations don't quite meet all of these requirments but are generally quite safe. Public buildings, street displays etc will generally conform though.

In a public display here you'll generally find a mix of 2 or even 3 voltages in use.

Strings that are up high over streets etc tend to be 220V (230V)
Large outdoor Xmas trees tend to be 110V centre tapped and other smaller displays are generally 24V. Building site displays e.g. on the top of tower craines are all 110V centre tapped.

Most domestic outdoor lighting is 24V or even 12V on smaller runs with individual plug-in xformers for each set.

For some reason ETCI does not approve of the use of 13A BS1363 weatherproofed sockets in any fixed wiring situation so you'll find a lot of CEE-17 outlets in use here where as in most other countries you'd find a simple weatherproofed schuko or BS1363 outlet. They get used for everything from providing powerpoints in gardens, xmas lighting, temp outdoor displays, outdoor PA systems, camping sites etc etc.

So you'll find BS1363 extension reels with a blue CEE-17 plug on the end or in some cases even full blue CEE-17 extension reels in use in newer buildings.

Supprisingly enough a CEE-17 reel made to a much higher standard than a typical BS1363 equivilant tends to retail at a much better value price and give you a much more flexible supply outside as it can supply up to 3KW safely.

We had a lot of problems vacuuming the car with various extension cords that tripped at less than 1900W (which is what the vacuum cleaner pulls at full power) so CEE-17 reels made a huge difference.. (you just use a short adaptor lead for the hoover.