How to programmatically read the display name of a CCK field from the allowed list?
You can use the following code.

$field = content_fields($field_name);
$function = $field['module'] . '_allowed_values';
$values = array_values(function_exists($function) ? $function($field) : (array) content_allowed_values($field));


This code is similar to the code used by optionwidgets_options(); the difference is that optionwidgets_options() returns also the value for the empty choice.

The output of content_allowed_values($field) is an array that in your case is the following one.

array(
  'US' =&gt; 'United States',
  'UK' =&gt; 'United Kingdom',
);


As you are only interested to the options visible in the user interface, I passed the result of content_allowed_values($field) to array_values().