End of this year I wish to come to the USA (I'm in the UK) to follow my adopted NFL team round for a full season. This means I will roughly be traveling to a new city every 1-2 weeks.
I tried doing this once before in 2001 and back then Internet wasn't big like now so all flights were booked by phone - calling different travel agents and companies to get quotes. By pure luck a lady in a call centre for KLM when I explained my plans informed me if I knew my exact dates she could add on internal flights with their US partner airline for a flat fee - back then was a very reasonable £40 per internal flight. This was amazing and though KLM was more for the same international flight than some of the agents only they being a direct airline could do this. So I went away and planed travel midweek to the cities where my team was playing. If the partner airline did not fly the route I had to buy 2 flights rather than go direct but at this price it was cheaper than going with a separately bought direct flight. It worked fantastic.
However when I tried to book similar a few years later I basically had people on the same KLM call line tell me I was mistaken (or insinuate I was blatantly lying), that it was impossible nothing like that ever existed to the public etc., etc., and no one - I repeat - no one, has ever heard the like I have ever told this to - so much so that if I had not done it myself personally I wouldn't believe it either.
So is there anything similar nowadays that I can do that will allow me to add on internal flights at a flat cost to my international ticket to make it one big multi leg ticket sort of thing to bring the internal flight costs down)?