It's not incorrect but it's dismissive of the thoughtful, hard work that's necessary to pull off a success. Every big opportunity doesn't equal a big win. Also, it's easy to take a hard-won effort for granted as an inevitability.
It's only dismissive if you think of events as having a single cause.
America's success relied, absolutely, on African slavery and on the removing the indigenous populations that were in its way. There are many other countries that engaged in slavery and population removal that didn't succeed to the extent America did, yes; you are correct. But there are also many other countries that simply had Enlightenment ideals and a democracy and didn't succeed to the extent America did, and many more that simply had thoughtful, hard work and didn't succeed at all.