If a PCT patent was filed in lets say "Ukraine" in 2004, but the owner let it never actually got it published as a patent in a national phase(in any country)legally may I file a similar patent in the USA?
The information you are giving us is a little confusing. A PCT patent application may be filed through almost every member-state (like Ukraine), but it will still be a PCT application and published with the prefix "WO". Is that what you meant?
Is there a PCT publication, in this respect? If so, regardless if it entered a national phase or not, it still is a published application and constitutes prior art.
On the other hand, noone stops you from filling a similar patent application in the US. Whether or not you will be able to overcome objections related to this prior art is a more complex matter. You will find it in your way, in any case.