Part of diplomacy is offering aid to those in need. Are you a potentially valuable ally?

Also good for training

Also if something fishy was happening to that massive stockpile of explosive material it's something that might wind up interesting the FBI for purely selfish domestic reasons.

I'm not sure if you are being serious or not, but I'm sure the US government is getting useful intelligence out of this as well. The US has an interest in knowing how this happened

> FBI has expertise to do my taxes

They do not.

If you want to invite the FBI over for a visit, it's easy enough: just report a major federal crime.