Remember that if you order a monitor from the EU you will probably need to buy a voltage transformer.
EU = 220v 50Hz AC
US = 110v 60Hz AC
I do not think either Philips or Commodore monitors are dual voltage (but I could be wrong)
Alexh is right. C= branded monitors are always "mono-voltage". But they will work with a simple voltage transformer.
Don't need to worry with the frequency difference on the power supply: the internal voltage circuit of monitors can cope nicely with either 50 or 60Hz (switched power supplies).
The same
could be not true for the video input: image don't fill the screen with Amiga in NTSC in a PAL monitor. Or image "over the edges" of the screen with a PAL Amiga using a NTSC monitor.
Open the monitor and tweak the trim-pots will fix it, of course.