My name is ***** ***** I am a US lawyer.
These sorts of determinations are very fact specific, so it's not possible for me to say how the Atlanta court is going to decide. Once you get your decision, under the Hague Convention, you are entitled to the return of your child. But it is not likely to be that simple, since you can expect the other parent to avail herself of the Atlanta courts to oppose any return of the child to the UK.
That means that along with your legal counsel in the UK, you're going to need a lawyer in Atlanta who is experienced in dealing with international abduction/Hague Convention law. If the child has been in the US for 15 months already, you can expect the other parent to assert amont other things that the child has settled in quite comfortably in the US and that it's in the child's best interest that he or she be able to remain in Atlanta. She may also assert that it was the intention of both of you that the child would be raised in the US and/or that you consented to your child's being taken to America.
I can't possibly possibley say what facts your ex will try to establish to show that she's entitled to keep the child in the States, but the mere fact that you were able to secure Hague documents in your favor is not automatically dispositive of the issue. It is likely only going to be the beginning of a complex court battle.
This overview on how to win an international custody case is very instructive.
I am not endorsing the law firm, about which I know nothing. But the article is detailed and thorough and points up all of the possible obstacles to your securing the return of your child and troubleshooting strategies to put yourself in the best position to win your case.
To find a lawyer in the Atlanta area who practices international family law you can contact the Georgia Bar Association's Lawyer Referral Service
. They charge a fee of about $50 for the referral which includes a half hour consultation, which you can have on the phone. Alternatively, you can use a commercial referral service such as Martindale.com
. Many of Martindale's lawyers are peer and client rated, which you might find useful.