My understanding is that in Russian, using "na" to refer to Ukraine implies that it is an "unbounded region." I.e., not a country. This gets translated to "the Ukraine."

It's like the difference between saying "Washington State," which is a political entity and "The Pacific Northwest," which is a region. You wouldn't say "the Washington State."

Before anyone says anything, in some cases the article is part of the country name. It's "The United States of America" and "The United Kingdom of Great Britain and Northern Ireland." But it's not "The France" or "The Germany."

So, yeah, calling it "the Ukraine" denies nationhood to the people of Ukraine.