What's the right default collating for MySQL?

I have the following

PHP 5.3.1
MySQL 5.1.41

I upgraded MySQL and found my key lengths were too long, I'd done encoding utf8. I found this, which explained the problem:

I installed MySQL with UTF-8 as the default character set for my databases.
Instead of modifying the installation sql file, you can create or modify
your database with latin1 as the default character.

Creating the database:

CREATE DATABASE 'db' DEFAULT CHARACTER SET latin1 COLLATE latin1_bin;

But the question is, I'm running a U.S.-based site. What's the proper character set for WordPress for a U.S. American English site?

Thanks!