The Sarao jeepney which is prominently featured in the film driven by Mon Confiado and ridden by Thomas Ian Griffith and other casts is a unique mass transport system in the Philippines and could not be seen anywhere in Vietnam.
Supposedly set in Vietnam, the final shootout takes place in a building where the signs are all in English. These signs should have been written in Vietnamese or at least French.
A car chase ends when the pursuers drive through broken glass and puncture their tires. However, when the car comes to a stop it is shown parked on top of the broken glass - given the chase speed, the car should have come to a stop well in front of the glass.
When the large-caliber machine gun is captured from the 'Vietnamese' troops and used against the ones conveniently lined up in a wooden shack, a close-up view of the front of the gun clearly shows the belt feeding it to be loaded with blanks, with the crimped ends.
When they throw the glass bottles out you can see they are San Miguel bottles from the Philippines.
The general awards are US medals.
Near the end of the film, Church yells "They're leaving!". Just after he does so, a film crew member's legs can be seen in the background underneath the vehicle that Church is taking cover behind.