The differences between NRA and DCRA service rifle matches are significant. The US rules favour the rifle; Canadian rules favour the shooter. To win in the US, you have to be well equipped within the rules, and be a very consistent position shooter; in Canada, you have to be a good shot with whatever rifle you show up with.
To illustrate, for a very long time, the US rules specified no externally visible modifications. The National Match rules let so guys shoot heavy barrels, stocks and fine adjust sights. The service rifles had to look off the rack, except for gaming the internals with lead weights under the handguards and in the butt trap. There were no restrictions on jackets, slings or mitts. Just about nothing military except for the outline of the rifle. In Canada, the military influences are still very strong. The courses of fire is nothing like in the US, with positions, fire-and-movement, teams, every size and shape of target, and no round bullseyes.
To get back to the original question, anyone can shoot at Perry. Join whatever organization you need to be eligible, pay the fees and show up. But, remember the US border doesn't let some of our stuff in, and vice versa coming back. Showing up with a Norinco will stop your trip at the border. But, a rack grade Springfield might not be competitive. A USGI Garand won't cause any ripples either way, but likewise unless you are very well practised, you will only be subsidizing the prize list with your entry.
PS - spend the $35 and get a copy of George West's book, "Mastering the Service Rifle, Competing and Winning with Military Rifles of the Past and Present". George shares the lessons he learned enroute to winning 2 Queen's Medals. He is, The Queens Medalist 86,87 on CGN.