Marc why is it that my JDM NSX can start up without me pressing down on the clutch pedal and why USDM cars can't? Why is there this difference?
You're too riced out. jkjk
There are several differences between JDM and USDM NSXs. One example is the ignition coils. JDM NSXs throughout 1991-2005 use 2 pin ignition coils while USDM NSXs changed to 3 pin.
As for your clutch pedal thing, for Japanese NSXs (this is why this product: https://www.mitamotorsports.com/1st-gen/239543057) or other Right Hand Drive clutch pedals cannot be installed as is, is because it has a clutch switch lever. This allows you to be able to just start the car without the pressing down the clutch. While USDM cars they do not have this lever.