Wishbone: Is there such a thing as a PAL or NTSC TV these days? Didn't we leave those concepts behind along with CRTs?
Nope.
Later CRTs in Europe actually supported both 50Hz and 60Hz (PAL 60Hz uses the NTSC 60Hz refresh rate with the PAL colour encoding systems), and indeed, if you had a GameCube in Europe with a TV that didn't support 60Hz, you were essentially fucked with games like Geist.
It's also worth bearing in mind that the WIi U does support standard def TVs, although I don't know how a 50Hz-only TV would process actual Wii U games, which run universally at 60Hz. In any case, the supposed reason why Nintendo kept VC games at 50 Hz was to cater for those with antiquated TVs.´Not sure why they'd assume that people with an antiquated SDTV would buy a Wii U, but anyway. Bizarre, but true.
Also, HDTV transmissions in Europe and the US still differ in that Europe still broadcasts in 50 Hz and the US still broadcasts in 60 Hz, so most HDTVs will support both refresh rates.