Are there too many commas in this sentence?

I moved to Huntington Beach, California, the home of my favorite band, Avenged Sevenfold, and started school there as a junior.

Are there too many commas in this sentence?

Grammatically speaking, every comma in that sentence is appropriately placed.

Stylistically speaking, some people find the use of "so many commas" to be offensive or distracting somehow. Since you are using commas for different purposes, you can make use of some other punctuation options for the different purposes.

The most obvious choice is to replace the "parenthetical commas" with actual parentheses:

I moved to Huntington Beach, California (the home of my favorite band, Avenged Sevenfold), and started school there as a junior.

Alternatively you could go with "parenthetical em-dashes":

I moved to Huntington Beach, California—the home of my favorite band, Avenged Sevenfold—and started school there as a junior.

Grammatically, no:

The first splits one geographic area from the larger geographic area it is contained in.

The next introduces a parenthetical clause, and the next a parenthetical clause within that, both of which are ended by the last.

All of these uses are grammatically normal.

Now, you might as a matter of style decide to remove them, by using parenthetical em dashes, or rewriting entirely. But one might also as a matter of style take the version of parenthetical em dashes and turn it into the version you have here.