Yes the hobby is dying, not just in the US but also in many other countries like the UK, Australia, Canada, etc.
Some might say it's not dying but changing. Changing for the good? No. Too many modellers who say something like that are in denial. The trick is to get the transmitter in as many hands and ASAP.
Are modelling organizations capable of doing that? Not so far. Modelling organizations and the RC aeromodelling industry have been hemorrhaging money for many years now, and membership has been dwindling just as long.

So, what could be done to rectify this situation? I have a readily available solution, but no one takes it seriously. One thing that modeling organizations could do and should have done decades ago is to place ads on TV. Too expensive? Mom and pop stores and any small business can afford to pay for TV ads, why not aeromodelling organizations? One organization lost over $30 million after 20 years and continues to lose over $1 million annually. After losing so much money preaching to the choir, depending on the location, even one local TV ad would reach thousands, if not millions, of people. You see multi-rotors on TV regularly.