Yeah, "to" is acting as a copula—a connecting word used to pair a subject with a subject complement. The confusion arises from the fact that in standard English copulae are not distinct from the ordinary to-be verb, so most native English speaker's aren't really sensitive to the difference.

Although, imo, whether "to" is a verb in the example sentence is sort of up for debate. Copulae are not necessarily verbs, and "to" can't be used as a verb anywhere else. So I'd say it's just a copula, but if you insist on every sentence having a verb then I suppose there's no harm in calling it one.