The U.S. DOT rolled back the 5 mph rear bumper impact standard in 1982, to 2.5 mph, but Canada retained their 8 km/h-5 mph standard until 2009. Some models came equipped to the higher standard in both countries, others were built to the more permissive U.S. regulation and sold that way in America. I can't speak specifically to the '86 Regal, but the differences weren't visible, the ones built to the higher standard used the same bumper, just the structure underneath was beefed up, and only the rear bumper was affected.
In '86, before daytime running lights, the only other differences were metric gauges and Canadian compliance labels.
In '86, before daytime running lights, the only other differences were metric gauges and Canadian compliance labels.