Oh for pities' sakes...
NTSC = mph
PAL = km/h (note that "kmh" and "kph" are not actual official measurements)
There is no way currently to switch from one system of measurement to the other within the game. Anyone who says it appears in the Options menu is talking out of their sitting organ - or just making stuff up to appear superior. I agree that I would like the option in the future, but it has not yet appeared in GT1, GT2, GT3, GTC2001, GTC2002 or GT4P. You can use the alternate measurements but it requires an Xport, a gamesave from another region and a Hex Editor.
It is true to say that some countries served by the NTSC television standard prefer to use kilometres and km/h, but get stuck with miles and mph (Canada is a case in point). It is also true to say that some countries served by the PAL television standard prefer to use miles and mph but get stuck with kilometres and km/h (the UK, for example). A switching option would be handy. Does anyone who actually cares about drag racing prefer the 0-400m test over an actual 1/4 mile? Would you rather have kW and Nm or hp and lbft?
And finally "English system"? Guess what? Whatever system of measurement you use - Imperial, US Imperial (although less so - it's derived from Imperial but the official measurements are kept in the US) or metric - it's French. Yes, French.