wp_editor() fields on Theme Options Page not saving

You need to add a name attribute to your editors. The name attribute needs to be set to the value of of your option, so like this:

function us_partners_cb() {
    $us_partners_desc = get_option( 'us_partners_desc' );
    echo wp_editor( $us_partners_desc, 'uspartnersdesc', array('textarea_name' => 'us_partners_desc')  );
}