The Mississippi river system is also very easy to get to through OTL's Chicago. The subcontinental divide is a mere handful of miles away from Lake Michigan and the Illinois River is a mere six mile portage. That opens up the entire Miss culture and eventually the gulf.
Yes, indeed, once you got the ships. My point was that the spread from the great lakes -> st.Lawrence -> Newfoundland etc offers a very good progression for boats to change into ships, each step further offering less sheltered waters and more challenges.