It is very hard for insurance companies to investigate and interpret services provided in other countries. This is a tough area for them - so make sure to work closely with them to provide them everything they need.
As with any insurance - they may determine what is "reasonable and customary" for the treatment received and may reimburse you that amount. Thus they may be requesting more information so they can see exactly what you had done.
In the US all bills for medical care use a universal billing code system. For example, the CPT code (universally used in the US) for a jaw x-ray is 70100. So if you lived in Oregon but got the x-ray in New York your insurance company could easily interpret what was done. If anything they'd need to see proof that you needed the x-ray.
However, someone who has a jaw x-ray in China (for example) wouldn't have the same "code". So some interpretation by the higher level claim folks (even SIU) is needed to flush out what really happened, etc. And, if your home country uses a different language than the country you live in - that requires even more work for the insurance company. It's hard to get medical information translated.
And, let's say your insurance company says $150 US dollars is the "usual and customary" fee for that service (again, only an example as I have no idea what the cost would be). And let's say the country you were in charges the equivalent of $350 US dollars for that service. The insurance company can say "we can only reimburse you $150.00".
It's not fraud until you accept funds you were not entitled to. So the worst that could happen is they deny all/some of the charges as they can not justify any/all of the charges.