Get Posts with specific custom value and specific category

I think this works:

<?php
$args=array(
  'showposts' => 3,
  'category__in' => array(3,5),
  'caller_get_posts'=>1
  'meta_key' => 'country',
  'meta_value' => 'USA'
);
$my_query = new WP_Query($args);
if( $my_query->have_posts() ) {
  while ($my_query->have_posts()) : $my_query->the_post(); ?>
    <p><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
<?php
  endwhile;
}
wp_reset_query();  // Restore global post data stomped by the_post().
}
?>

Hi MichaelH, Thanks for your input, I tried that, it works but my requirement is a bit different

I am looking to add this code to index.php, category.php

country is added as a custom field.

The site works as usual wp install, and when the user selects a particular country then it keeps the country in a session variable. Again the site works normally but only the posts for that country are displayed.

I added this

$args=array(
  'showposts' => 3,
  'category__in' => array(3,5),
  'caller_get_posts'=>1
  'meta_key' => 'country',
  'meta_value' => 'MY SESS Variable here'
);

It is not working when I select a category (I replaced ‘category__in’=>$catid with is_category() )

//if category archive assign queried category
if ( is_category() ) {
$catid = get_query_var('cat');
}
$args=array(
  'showposts' => 3,
  'category__in' => array($catid),
  'caller_get_posts'=>1
  'meta_key' => 'country',
  'meta_value' => 'MY SESS Variable here'
);