[tsukikage]

I can't speak for YC applications, however day to day in my workplace I am surrounded by engineers for whom English is a second language (and, for that matter, also native speakers with strong regional accents); I also regularly interview such.

I find that speaking with an accent is generally independent of the ability to clearly, fluidly communicate, which is actually what is important.

Do you frequently find yourself pausing mid-speech to think of the term you need? Do you frequently find yourself struggling to understand idiom-laced speech? Do you frequently find yourself talking at cross purposes with people because you have used a term with a different meaning to the one you intended, or have failed to correctly understand a term they have used?

These and similar problems can represent genuine failings of communication that may become an issue. It is usually obvious partway through a discussion or interview if this sort of thing is likely to be a problem: they hinder the candidate telling you about themselves and/or answering the questions they are asked.

If you do not experience this class of problem - if you are merely concerned about unusual stress/pronunciation or similar, but do not have trouble making yourself understood, understanding your interlocutor, or speaking at a sensible rate - then I suggest you should not worry about your accent, and it would actually be to your benefit to contribute significantly to the video, in order to demonstrate that there are no significant communication issues to anyone who may otherwise be concerned.

EDIT: PG says similar things here: http://www.paulgraham.com/accents.html