Yes, US used different approach. I don't have the answer to that, but I guessed they used different metal alloy of high heat resistence, The darker color metal fitting at the F-15E's gun muzzle looks different from the aluminum panel.
Even Mig-29 also don't seem to use titanium. I think Sukhoi's design is perculiar to Flankers and its variants.
Sorry for the blurry post. Mig-29 does have Titanium around the gun muzzle, just smaller.