Multisite – Getting Meta query to select from wp_2 tables

by

From what I understood, you want to get products on US site from UK site.

You can use switch_to_blog() to direct your queries to your sub-site. This function uses blog_id as parameter.

So, in your case, 

switch_to_blog(2);
//your code to fetch data
restore_current_blog(); //this restores query to current sub-site.

See documentation: https://developer.wordpress.org/reference/functions/switch_to_blog/