I think to drive
@mattikake's point home we should be comparing the NON LMP, NON Prototype, NON F1 cars, outside of WRC (no rally racing).
Then we see how many wins Japanese cars have as a whole. From what a remember its not too many when racing with Corvette, 911, BMW, etc cars. These cars that race the Viper GTS-R, Corvette C5R/C6R/C7R, 911, Ford GTLM, etc, those classes, no Japanese cars are competing. They probably win at the compact and sub compact level, but at the R35 GTR, NSX, Supra level they AREN'T racing the brands we know that have been dominating.
I mean someone show me a Ford GTLM, C8R, 911 RSR class cars and a Japanese car racing them. I dont think theres any, is there?
Also, as far as the OP is concerned, the C7Z is a hard car to drive 10/10ths. It has a ton of torque and easy to spin. Theres a video online that exaggerates this when they compared it to a GT350R and an ACR. The Z06 just spun, exaggeration, I know. You have to be a really good drive to wring out that cars potential, then theres the over heating issue. Its so bad a ZL1 performs better despite weight in 300+ lbs more. GM fixed this with the ZR1.