The US has Customs and Immigration facilities in Canada, the Caribbean, Ireland, and now the UAE. I would say this option is mostly a positive, though the new one in UAE has had some teething issues for sure. I was curious if any other nations offered similar facilities in other countries. I know the US arrangements are reciprocal, so in theory Canada could set up preclearance facilities in Newark Airport, but chooses not to, likely due to the cost. The UAE facility only happened because the UAE government offered to cover the $5 million annual costs of the facility (they were ultimately allowed to cover 85% of the costs due to Agricultural inspection costs not legally allowed to be reimbursed under US law). The US says an airport needs 400,000 annual travelers to the US to make it viable, so it would seem that places like Newark, which has over 1 million travelers to Canada per year, would be ideally suited for a Canadian facility. Or if India were to set up a preclearance facility in the UAE, where nearly 5 million people travel to India every year, it would certainly have its pluses and minuses, but overall I think would be beneficial to most people.