I don't know all of the differences but after searching for 2 minutes I found this info
udsm ITR front end= round head lights 98+ front end with type r lip

edm, jdm itr font end: bar style head lights
on the jdm motor you will find
- LSD
- 2.5" collector of header
- JDM and USDM have different sized letters on DOHC and VTEC
- PR3 on head
- P73 on distributor
- bronze shift linkage
- dual valve spring
- JDM - B18C vs B18C5 - USDM
-most JDM type R motors will have a green stripe of paint on the back side of the distributor
96 & 97 JDM ITR heads have the same cams as 97/98/99 USDM cams. 00 USDM cams are the same as 98Spec JDM ITR cams and JDM CTR cams, they basically have 3 degrees more duration on the intake cam, the exhaust cams for all ITR/CTR are the same regardless of year/country. 96 spec ITR heads had a hand port and polish, 98spec ITR were machine polished
JDM GSR has a 10.6:1 compression ratio, and 180hp 126lb-ft.(??)
JDM GSR has the p72 head and cams and IM&TB, different pistons, rods, and crank.
USDM ITR motor has 10.6:1 compression 190hp (??)tq.
ported and polished PR3 head, different TB and larger bore TB
coated pistons, different rods, and crank.