3 days unless I can rig a way to distill drinkable water and fuel the process indefinitely, then a few weeks until I starve unless I can figure out food too. Depends on how big the island is I guess: If there's enough to hunt, trap, and forage, I might actually be OK at least until I get sick or injured.
Some things have definitely changed: Renewables are now cheaper than fossil fuels, there are multiple countries that have achieved extended periods of being completely fueled by renewables, and the impacts are climate change are being felt more keenly by everyone.
We still face a very strong possibility of an incredibly bleak future, but even now it is not assured and many things have changed in the last decade (for better and worse).
The gun violence is a symptom of a dysfunctional society, not the cause. If the US was more equitable for everyone in terms of money and healthcare, it would go down.
Nothing against sensible gun regulations, but even if you magically disappeared every gun in the country, the problems that mess people up so bad they get violent would remain.
Needle nose pliers