They did try different costumes but none were Wonder Woman. Perez updated origin worked wonders in explaining her costume in a neat way.
"The American theme of Diana's costume was explained by Pérez in the Challenge of the Gods storyline in which Diana engaged in a series of trials arranged by Zeus as punishment for refusing his advances. Diana met the spirit of Steve Trevor's mother, Diana Trevor, who was clad in armor identical to her own. Trevor revealed that during World War II she had crashed on Themyscira while on duty as an US Army pilot. She blundered into an Amazon battle against Cottus, a multi-armed demon, at the portal to the underworld. Trevor was drawn into the battle, although she was armed only with her side arm. She wounded the beast before suffering a mortal blow, allowing the Amazons to reseal the portal.
The Amazons, impressed by this unknown woman's self-sacrifice, entombed her with honors and clothed her in armor displaying the American flag pattern on her uniform (which they assumed were her heraldic colors). Consequently, Princess Diana's costume honors Diana Trevor and, by clothing her in its own heraldry, was intended to ease the heroine's acceptance in Man's world."
Now, through out the series her costume has been a focal point of discussion amongst other countries believing she's too pro-USA and has provided some good conflict. Also, I think her wearing the colors is even more important in this day in age. There's a lot about American Values in the country and for me Wonder Woman represents what the values need to be. An understanding of one another. Here's a woman from alternative life style of sorts. DC doesn't come out and say it but Wonder Woman is from an island populated by women, many of which you would expect to be gay(though I think they've only feature one true couple). Also writers who have written her have remarked or even put in print the idea of her being bi-sexual. She's not Christian, she prays to Greek gods. Wonder Woman promotes tolerance and moving forward. DC talks of her not just as an ambassador of her country to the world, but as an activist. The US is her adopted home, and I like the idea that she wears the colors of the USA being she's the kind of person who'd get bad mouthed on talk news now. Greg Rucka did some good stuff with this in his run.
I'm not one of theses "USA is the best nation ever" type of guys. I listen to my Rage Against the Machine or KMFDM and am a faux goth of sorts. I like what Diana stands for, and I like to think of her as what a true model American should be.
(Minus snapping evil doers necks. Though Max Lords had it coming)