I pack heavier than you, but I have seen several bike tourists on road bikes, either with bikepacking setups or with trailers. And they appeared to be having a great time.

But, if you really want to use a road bike, since a lot of road bikes lack the really low gears that are commonly desired for touring, have you thought about your gears and whether or not your gears are low enough for the route?

I attached two photos below of a couple I met in Iceland that were using their Ritchey Breakaway bikes for a tour. I cropped out the faces since I did not ask permission to post photos.






Although they were packed for only a two week tour, not as long as you would be riding, I find that once I have a week worth of stuff, a longer trip does not need much more stuff.

If you wanted to go with rear panniers on the bike, I would suggest you try to move some of the weight further forward, either supported from the handlebars or with a frame bag or both.

If you can't fit fenders due to tight tire clearance, you might consider race blade fenders. I have toured without fenders and it can be quite a mess. The Pro XL version fit nicely on my 28mm wide tires on my road bike.

For a cross continent trip, there may be times you need to carry a lot more food and water, so that would be a consideration.

If I recall correctly, you posted on Crazy Guy on how you did your light weight touring, if so the OP might benefit from the link.