As I have said multiple times, Doom is not an event, it is a process. IMHO the Doom we all speak of began for the USA around 1980 and has been gaining momentuum gradually since then.
That momentuum however, is positively OWNED by the momentuum of 330 Million citizens getting up and going to work everyday. I was reminded of this once again as I returned from Wisconsin after visiting the Grandkids between Thanksgiving and Christmas. We took off from Chicago after dark:

...and flew west, arriving at Silicon Valley also after dark:

...and in between, we saw many other places:

My point would be, that the efforts and desires and dreams of 330 million people are a mighty force to be reckoned with. It will not be derailed, it will not be crashed, and it will not even take much notice of Donald Trump and all his greedy minions, leastaways no more than it would have noticed Killary and her murderous ways and greed, possibly even greater than that of the Donald.
Make no mistake, I ABSOLUTELY AM a believer in Doom. We ARE SO SCREWED when we run out of FF's to burn, and carbon to spew into the air. The backlash from the sudden cessation of FF burning will almost certainly provoke the next Ice Age, and we will gradually slide down into 50,000 years (more likely 80,000 years) of ice and the global ecology will RESET.
Because, you see, all that carbon dioxide is the only thing saving our fat and lazy behinds now.
My best guess as to WHEN this will happen is on the order of 120 years. Note I did not say "the close order of", which means I don't expect it in less than 12 years or more than 1200 years. Note also that this is a far more pessimistic interpretation than my former bounds of 20 and 2000 years, with the mean at 200. Because you see, I am getting fearful and cranky and just plain tired in my old age.
Sorry, but the accuracy of the data allows no closer estimate. The primary date is and always will be dominated by human psychology, how we respond to the initial hardships. This dominant factor is why exactly NONE of the economic models we bandy about here are worth a heartfelt "Damnation!".
Since I by and large consider both the R's and the D's as equally harmful to the USA, and believe that both political parties are SO OBSOLETE and SO HARMFUL to my beloved country, I'll have to say that which party controls the US government and when and for how long, is largely irrelevent. The optimal state IMHO is when the damage they do is minimalized by swapping dominance every 4-12 years.