We happen to love Rhode Island and there's a ton to see and do from beaches to mansions to quirky hot dog stands. But if you absolutely MUST see the rest of the northeast, New England is the size of a walnut, and pretty much anywhere you'd want to go is an easy day trip. From RI, Boston is about an hour, New Hampshire and Vermont are 2-3h depending on what you'd want to see, and southern Maine is about 4h. Heck, Montreal and Quebec are a short drive as is NYC. You get it.