Paris, Rome, and London are larger travel markets than Lisbon, so your findings sound very intuitive. There is no generalizable answer to your question. Your connections and the convenience/lack thereof really depend on where you're starting from. Flights originating from Seattle probably have some characteristics that aren't replicated than, say, Los Angeles, or Philadelphia or where I live (Washington DC market - 3 airports). But you don't have much choice, do you? I doubt Portland would have better choices than Seattle. Obviously if there were more people flying from where you are to Lisbon, you'd have better choices of flight and connection times. Sorry...I know this doesn't make anything better. I tried to find flights to Bucharest from where I am and, like you, have to deal with unfavorable connections (I'll likely be doing the Turkish Air layover in Istanbul).
PS. As a somewhat related trivia, these states have the highest Portuguese populations in the US (I'm from Poland so Chicago ORD is a major base for us flying home to see family).
Rhode Island: 99,445.
New Jersey: 78,196.