You're right about the drift in meaning of the word "liberal" -- and probably will be right about the other terms.
The notion of a "left-right" spectrum in politics is misleading in its simplicity. Politics is not two-dimensional. In any "first-past-the-post" electoral system, successful political parties are colitions, rather than expressions of a coherent ideology. All the more so in the U.S., where there can only be one President.
Similarly, there is no one-to-one mapping of "liberal" to "Democrat", nor "conservative" to "Republican" (different names -- same principles in Canada). As the ingredients in a winning colation change over time; so too will the meanings of all the convenient labels we attach to the parties and driving ideologies.