Change order of flags

There is an filter ‘langbf_countries’, so you can apply your sorting method:

function my_countries_sort( $countries, $region, $language ) {

  // DO SOME SORTING

  return $countries;
}
add_filter( 'langbf_countries', 'my_countries_sort', 10, 3 );

Also, created ticket for 1.1 milestone: https://github.com/meloniq/language-bar-flags/issues/8

Hi…i just need 3 flags to be presented on header ( USA / MEX / BRazil ) in this order.

How can i do it?

same way is told in your post above by meloniq