IAH-E and EWR C-3 were built with sterile transit lounges, but these were never used after the sterile transit/TWOV program was scrapped post-9/11. Reportedly, the EWR space will be redeveloped into a United Club, but I’m not sure of the status of the IAH facility. I believe other such facilities exist in the US, but CO was a strong proponent of international-to-international transit over its hubs, hence the investment.