Hi Alex,
technically there is no problem using EU transmitters with US receivers. The other way around is different, as there are some frequencies around 606-614Mhz (?) blocked on US transmitters. But my MCR42S (US model) receives everything within it's stated bandwidth. If you want to use the EU frequency table on the US model you have to reprogram the receiver. That's a bit of work with the Wisycom Windows software. But I did it and I use the typical EU 8Mhz-TV-Channel layout on a US receiver - instead of the 6Mhz-TV-channel layout of the US models.
If you need help with the frequency tables and the programming, you can contact me. You need an USB infrared programmer for that.
One side note: early versions of the US models ( MCR42S ) are NOT able to switch compander to receive other transmitters from Sennheiser or Audio Limited..
That might be the reason why you get them for less money. The EU models (and maybe the later US model ?) have this feature.
I own an EU and an older (and reprogrammed) US MCR42S. They look and behave the same. They both run the latest firmware.
Just with the difference, that my US MCR42 doen't show in the menu the different companders like the EU model.
The US Model just let me choose between the 2 Wisycom companders: "ENC" and "ENR"