First, it is quite unlikely that a US court would take on the case. Someone will have more details, but for example in EU law if you move away from the place you last lived together, you can only file for divorce in the country where your partner is living (in this case, India). Annullment is a much more serious matter than divorce, so I doubt any American court would take this case: Annulment would mean that a US court would have to decide that an Indian registry office didn't do its job right.
Second, A needs convincing evidence. Frankly, "masculine appearance" and "typical masculine voice" are just opinions and therefore not evidence. Even if the court were convinced that B has a "masculine appearance" that's not evidence for being a male. A has to show the evidence, and as half of us know and the other half learned in their biology lessons, there is some pretty convincing evidence that someone is a man which A didnt' mention. And I'd ask anyone not to edit this out, because it is quite essential to the case. B doesn't have to visit a doctor and get a statement that she is a woman (which would destroy any case immediately), because based on the available evidence, A will lose the case anyway.
On the other hand, after that court case has finished, B can at any time (after appropriate waiting times according to US law) come to the USA and file for divorce.