Unless you know the regulations in detail, don't take fruit or vegetables into Canada or back into the US as well. The restrictions are quite different in each direction. Meat into Canada is okay but there are some restrictions going into the US. There are some quantity limits into Canada, but unless you have a monster-sized family, you should be okay. We've never, ever been checked on quantities. We find it's just too complicated to take the risk of making an error so never take any fruit or vegetables across in either direction.
If you have dog food, you should declare it but have never had problems going back into Canada, but you MUST declare it going into the US and it must be in he original sealed bag. Make sure your dogs shots are up to date (should do anyway) and have the vacc. papers.
There's alcohol limits into Canada which are very restrictive. Unless you know the rules for sure, it's best to buy in Canada and pay our mafia inspired liquor prices.
If you have to bring any medications, make sure they are all in the original containers from the pharmacy with doctor's name, etc. Just in case you ever happen to be searched. We got searched once into the US for forgetting to declare dog food and you never know what little thing will get you tripped up. Be 100% honest at all times and never try to hide anything, ever. They do occasionally throw some oddball questions at you seemingly out of the blue so you should know everything that you have with you in your RV.
We have all the usual American chain and big box stores here. Most of our TV shows are American. Most of us all drive American trucks and there's a lot of US made cars on the road. You'll find a Wendy's or McDonald's all over the place when you get hungry on the road. You'll feel right at home.
If you have a big, you might try and find out if some of the crossings are easier for bigger RVs. We have one here near Vancouver that is extremely tight to get through. At some of the crossings, they'll send you through the commercial lane which is a LOT easier to get through.
Gas is currently almost 50% more expensive than in the US so fuel up before you get here.
I'm not sure what Americans pay for duty on purchases made here in Canada so you might research that before you go back or what the exemptions/limits are for how long you have been out of the US.
Otherwise, things are pretty straightforward. We cross back and forth across the border all the time and we have a membership in a campground on the US side of the border that we camp at a lot. Except for our dog food incident, we've never had any problems whatsoever. We do have Nexus cards though.
The border folks are usually easier on RV-ers. We're on average, older, wiser and more responsible...