On the subject of czars...why would anyone even suggest such a stupid title for an American appointed position that has been used previously to describe an autocratic emperor selected by heredity? It's America! Not Russia! But I digress.
If you use a definition of empire that is not limited to simply the title of an autocratic ruler, but rather the dominance of one country over another, non-native region in domestic and international affairs, you could say Britain, France, and Spain are still empires. They control territories in South America and various island chains that are not part of the proper country. Likewise, the United States owns Puerto Rico, Guam, and a host of other locales that are not states (and thus not participating in the United States government directly, but are still dominated by the US government). Does that make the United States an empire? I would say so, at least in a vague sense.
If you use a definition of empire that is not limited to simply the title of an autocratic ruler, but rather the dominance of one country over another, non-native region in domestic and international affairs, you could say Britain, France, and Spain are still empires. They control territories in South America and various island chains that are not part of the proper country. Likewise, the United States owns Puerto Rico, Guam, and a host of other locales that are not states (and thus not participating in the United States government directly, but are still dominated by the US government). Does that make the United States an empire? I would say so, at least in a vague sense.