US LLC can be taxed as a pass-through entity (taxes are paid as if the owner of the LLC had sent the invoice), or as a corporation (LLC is taxed as an entity of its own).
Best option for you is probably to make the US LLC transparent, then you pay tax where the owner is.
You can use the UAE company as the owner of the LLC, then - for the US tax authorities - it will be the same as if you had sent the invoice from the UAE company. But there is something called Effectively Connected Income (ECI), which is money you︀ make from "doing business in the US". Usually, when you don't work from US soil,︁ it is not ECI. But some people say there could be some hypothetical risk, especially︂ if you sometimes travel to the US etc.
If there is ECI, then there is︃ US tax. And if there is ECI and the LLC is owned by a company︄ (instead of an individual person), then there is something called branch profit tax on top︅ of it.
But there probably won't be any ECI anyway. I'm still mentioning it just︆ in case.
That's the US side.
Then there is the UAE side - no tax︇ (unless something changes), should be good.
But then there is the Ukrainian side. If you︈ were living in a high-tax Western country, your US or UAE company would still have︉ to pay tax where you are. You cannot avoid taxes by simply registering a company︊ in a country without taxes, it's not that simple.
I would assume it's the same︋ in Ukraine - in theory. But probably enforcement is very lax. They have other stuff︌ on there mind, and if you should get caught (unlikely), you could probably just bribe︍ them to let you off the hook?
So in that case, why bother with a︎ UAE company? Just set up a US LLC with yourself as the owner? You can️ choose a state where your identity doesn't appear on the internet (Wyoming or New Mexico, for example, I think).
Should be good enough?