As an international instructor, should I openly talk about my accent?

Accents are tricky, especially in large lecture halls where students hear you over a mic, and can't see your lips. Different regions might have different opinions on what accents are difficult, depending on what other native language groups the undergrads may have been exposed to.

In my opinion, it would go a long way for your undergraduates to say something like:

As you may have noticed, English isn't my first language. I know sometimes that makes it hard to understand certain words. Please don't hesitate to ask me to repeat something.

This might help with students who are shy or don't want to offend you by asking.

If you like, you could mention the other languages you're familiar with to encourage speakers of those languages to connect with you, or just as a fun fact (personally, I'd be curious to know). I wouldn't mention it to make yourself seem somehow better than them, as that could needlessly add feelings of resentment.

A difference isn't a weakness. Don't think of it that way. You may find difficulty in communicating because of that difference, but it is just that, a difference. People in the US from Alabama and those from Boston speak English with different accent and different idioms. Eventually we get used to hearing a different accent so the effect lessens.

In fact, you and I would have a lot of trouble communicating since I am quite deaf and technological solutions are only partial. Even it the best of situations a speaker sometimes needs to repeat or - better - say an equivalent thing with different words.

But the first few minutes is, IMO, a good time to introduce yourself and how you speak. In fact, it can be fun if you "put on" an extreme version of your accent, just to show the range. Cockney slang, for example.

I'm Australian and teach, 9 years, Engineering related subjects in Australia to students of a wide range of International backgrounds. In the process of introducing myself at the start of the semester I ask the students to put up their hand if they know what a dunny is. Most do not. I then explain that although I try to keep to normal English, occasionally I slip into colloquial Australian English. Due to this the students should show NO hesitation in asking me to explain/repeat/expand on anything I'm talking about. They will not offend me by doing so.

I emphasise that I do not want anyone failing because they could not understand me. For some students this appears almost liberating, to others, they still just sit there, eyes rolled back in their head, as per normal

In closing, my advise, if you are confident in your knowledge and are fine with the occasional question from the students, put it out there at the start of the semester and the students will respect you more.