I'm pretty sure anywhere there is a functioning port or navigable water way the number of trees within a day's walk is insufficient to support the needs of the population that humanity would need in that location to restart civilization. The fact that you can get in your car and drive to a beautiful forest doesn't actually help much.

Nonsense. You really should go take a good look at Google Earth. I come from a major port city in a first world country and literally right outside the city's urban area start forests that stretch for hundreds of kilometres. I know for a fact that many other cities like this along coastlines exist.

Amazon, Africa, ....

And you underestimate how quickly forests will grow back. Sure, it will take maybe 100 years, but civilization was built in 4000, so there is no rush.

Also, Saudi Arabia is sitting on an ocean of oil, not that hard to extract.