It doesn’t matter where your game sells, it doesn’t matter what your game does, it doesn’t matter whether your game is “free” to download with in-game purchases, whether it has subscription fees, or whether you charge for a disc containing the game, it doesn’t matter whether your game is version 4 or version 5 of the engine, it doesn’t matter what your immigration status is or which country you live in.
If your game generates at least a milliion bucks of revenue, however it’s doing that, then you owe EPIC their licensing fees. They may or may not “find out” about it right away; it’s up to you to be honest and actually forward the money to them once you hit the limit. If you don’t, and they come after you in court, the court will likely find that you were willfully infringing their rights, which is much more expensive than paying EPIC their 5%.
And, yes, there are many ways they can use to find out – platform partners, social media, game store resports, engine telemetry, crash reporter analytics, …
Purely mechanically, when you send them the money, they may require an ITIN (I don’t actually know whether this is still the case for people outside the US,) but as you claim you have one alread, that won’t be a problem.
Also note: The “1 million in sales” counts before Apple takes their pound of flesh, and before the IRS withholding happens, and whatever other costs and discounts you end up having. 1 million gross receipts, attributable to your game in any way, is generally believed to be the limit (at least last I looked – may have changed.)