The phrase "late capitalism" itself has been used for just over a century now[0]; while I believe the USA is destroying what made the nation successful and will therefore probably[1] go into decline before 2035, there's no particular reason to tie the weird aspects of the economic system to the USA's political nonsense.
Also, the USSR would be the opposite example of your first sentence, as the collapse was a big surprise to everyone (both inside and outside the bloc) even a few years before it happened.
The Roman Empire would be the example for long-term decline, as that took one or more centuries depending on where you count the zenith (180 CE to 376 CE as the start, the Western Roman Empire was definitely dead by 476 CE).
But you seem to want to present it as a "in our lifetime" kind of thing; for that, I would suggest the British Empire, which peaked just before WW1, yet was obviously a broken power by the time of the Suez Crisis of 1956 just 42 years later though full decolonisation took longer (and if you ask Sinn Féin, Plaid Cymru, and the SNP, isn't really finished).
[0] https://en.wikipedia.org/wiki/Late_capitalism
[1] There's a very narrow path where enough anti-corruption votes combine for a government which does something that, ironically, Trump promised in his first term: "drain the swamp". It can't just be "Dems win", it has to be broad consensus that not only takes this seriously but also is seen by the world to do so.
You're going to lose everything and your children will have no future. When they're old they'll be speaking from a similar perspective to the people who lived through the decline and fall of the USSR. Keep coping though.