Lots of data to comprehend. Looking at the ramifications of just two data points.....
(1) Total passengers for June = 844,994
(2) International passengers for June = 5,452
Some simple math = (5,452 / 844,994) x 100 = 0.645%
Ramification = Around 2/3rds of 1% of ABIA passengers are on international flights.
Therefore, it would be a waste of the airport's and city's money to add to US Customs facilities at the airport.
Some more math and an additional data point...
(3) SW Airlines 737 capacity = 115 passengers.
5,452 / 115 = 47.408 international planes.
Admitting that not every international flight is full, the fact that just two international flights per day should easily handle this market. Therefore, just one gate and one customs official should be able to handle ABIA daily international passengers.
While it's true F1 would overload that small a staff and facilities, additional F1 traffic only occurs one weekend a year. How would you keep any additional staff and facilities busy the remaining 51 weeks a year?
Do you build airport facilities up to handle projected traffic one weekend a year, or for the actual traffic the rest of the year? I suggest the efficent answer would be for the other 51 weekends a year.