The US has been tumbling pretty badly in most international sports. For men, an American hasn't been consistently in the top 10 in tennis or won a grand slam for like 15 years.
The younger generations in the US are probably the softest in the country's history and celebrate mediocrity. Sports greatness is mostly for people whose families have been in poverty in the last generation or 2, with a few exceptions. Africa and Eastern Europe have had severe poverty in this lifetime, so dedication to sports with few other better ways to spring out of poverty makes sense.
Why aren't Lewis and Jones American? If we can't count non white people or anybody whose families came to the US in the last few generations, we're digging from a very small pool of people. The US population was half what it is now just 50 years ago, and like 20% of them weren't white. Neither Jones nor Lewis have any recent immigrants in their families.
And why would it be Rousey and Dillashaw that you think "Americans embraced", and not any of the subsequent champs in their own divisions? Rousey lost to Holm and Holm lost to Meisha Tate, both Americans, and Cody Garbrandt was champ at 135 as well as the current champ.
Chris Weidman was champ at 185, Luke Rockhold was champ at MW as well, DC was champ at 205, Robbie Lawler, Hendricks at 170, Alvarez at 155, Holloway at 145, MM at 125, Lesnar at HW. There have been a lot of American champs over the last decade.
