Do I have a right to be upset?
if he's not in the USA you HAVE full custody. And if he's an absent parent, he is. The best advice i can give is to be a respectful and decent role model to your child. This also means no critical talk about his father. Let him make up his own mind about his father. Believe me, kids can think for themselves! Mine did! go to court if you have to. I might. just take great care of YOU and the child. Your son depends on you to show him the right way to behave. I know you can be a great mom (and that you are, already!)
He's in at least one other country? File!!
You can be upset all you want, but being upset doesn't get things done. If you are thinking about taking legal action, consult a lawyer.