Marlelar,
I asked my son who lives in NE-USA and he said:
To be honest, as far as I know, there really isn't a lot of Catholic sites worth seeing in New England. New England has a very strong puritan history where Catholics were looked down upon and even persecuted. I think in more recent times, because of WWI and WWII, there were a lot of Irish and Italian immigrants in the Boston area.
I think the only thing I would suggest might be the shrine of the North American martyrs in up state New York. We went there once and the site is nice but the main Church is pretty modern even though I think it was built in the 50's. A lot of the historical sights here are from the puritan "pilgrims" setting.