My best guess is that a public school with a good gifted program would have been an improvement, but one without would have been worse than what I experienced.
Good thing you were homeschooled then. The latter is much more common than the former.
public school with a good gifted program
What is this mythical thing you speak of? Oh, wait, you did say "America".
At the risk of being annoying by repeating myself on this point: Outside the US, UK and Tokyo (and more recently some parts of China), there is no such thing as "public schools with good gifted programs".
In fact, for most of the population, there is simply no such thing as "public schools with gifted programs". I suspect that for a significant fraction of countries, you could even drop the "public" part altogether.
On another note, most of the "Cons" listed after "After Algebra II, you're on your own" seem to be situational and just as likely to occur in a public school as in homeschooling. Including the part about a sense of position. Public high schools don't always give you a good accurate sense of your position applied in the real world, they usually instead give you a sense of how much things are broken.
So all in all, I'd say as far as education goes for most people in the world, or even for most people in first-world countries, or even for most middle-class-or-higher children living in urban environments, if the listed cons are really the worst of it then you've had a comparatively superb education.
At the risk of being annoying by repeating myself on this point: Outside the US, UK and Tokyo (and more recently some parts of China), there is no such thing as "public schools with good gifted programs".
To add to the other countries people have mentioned, Australia has them too.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.