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add_filter( 'woocommerce_package_rates', 'wcsupport_no_usps_us', 10, 2 );
function wcsupport_no_usps_us( $rates, $package ) {

  if ( WC()->customer->shipping_country == 'US' ) {
    foreach( $rates as $key => $rate ) {
      if (strpos($key,'usps') !== false) {
        unset( $rates[$key] );
      }
    }
  }
  
  return $rates;

}