The person who corrected your text to 'I love the Russian winter' was right to do so. 'I love Russian winter' is incorrect. Looking at your notebook entry, I also noticed that the first correction was made by Leigh Mumford, a native speaker and very experienced English teacher. Leigh's corrections are well known and respected on this site. The second was made by a non-native whose first language also causes problems with article use. I noticed that this second person also failed to correct another error 'I want to listen to Russian folklore song'. This is also incorrect. As Leigh pointed out in her correction, this should be ' I want to listen to a Russian folklore song'. Please be aware that not all corrections here on italki are correct, especially if they are made by non-native speakers.

Paul O'Neill's answer is correct.

This is a case where you can say it either way. They have the same meaning.

Sometimes it is difficult to correct every error, and sometimes there are different ways to say the same things. For example, 'I love Russian winters', or 'I love winters in Russia', and 'I love the winter in Russia'. Adding THE was the correct form for your sentence, but the meaning is understood either way.

I know we've confused you again, so let me add a more detailed explanation. When using an adjective derived from a country name, it is very common, if not usual, to omit the "the." "I love American culture." "I love French food. " " I love Russian vodka." This can also be done in other situations when you are referring to a general situation and not a specific set or group of the object. "I love red cars." meaning my general preference is for red cars. "I love the red cars over there." meaning that I like those particular red cars. So, in summary, if you omit the "the" before the noun, it carries the meaning of "all of them" or "most of them" or some other idea of a general feeling. When you use the "the", it carries the meaning of "some" and that you are referring to a specific group of the noun. Now, as I said before, in the case of your example, you will hear it both ways, but more commonly without the "the" for the reasons I have given