To avoid Canada and still see the Niagara Falls follow the ACA route until the intersection of Military rd and Upper Mountain RD, just before the on ramp to Canada.
Make a right on Military Rd. Take to end and make a left on Rt 104
Stay on RT 104 past Niagara University, enter the Devils hole parking lot on Right go over curb and cross over pedistrian bridge. Keep river on right and this path past the george Trail keyosk, you will pass another pedistrian bridge but instead of taking the main path to the end, take the one to the right, it goes down under the rainbow bridge, keeping the river on the right you will find a path that will take you to Buffalo Ave at I-190, the path ends here. An option is to cross over Grand Island, you will need to use Google maps to map this as I have never ridden on the Island. Or make a right on Buffalo ave. Take this to river road at a 4 way stop, it has a Overpass just after the stop. Make a right on river road. a couple of miles down river road you will see a park on the right and a bike path will be on the right. Take the bike path. This will take you to tonawanda creek, Take the bridge directly in front of you using the side walk, just after the bridge, take a right on the path and then a left at the river. Take this path all the way around to buffalo. take a left on Hertel ave and then a right on Niagara St. Stay on Niagara Street and follow the detour (signed for bicyclists) It will take you past the entrance to the Peace Bridge and will meet up with the ACA route.
Any further question please ask.