Will an SNES (US) work in Europe (Romania) or do I a need PAL version? (Why?) (Note: I will use AV cables.)
If you Google your problem, you can find many people with your same issue.
It seems to be possibile, but the main problem is that the NTSC SNES is expecting 110V while the European power will be 220V-230V and that's not good for it. So you may need a power supply or a kind of transformer.
Another problem is that the 2 consoles run with different vertical frequencies: NTSC has 60 Hz, PAL has 50Hz. (See here)
Of course you also need a TV that supports NTSC input, and an American SNES will need American cartridges, too.