In an interview Joe Biden complains about Russian interference in previous elections. He then says they wouldn’t interfere in U.S. elections under his tenure. Of course the election of 2016, and any Russian interference during it, happened during his tenure as Vice President.
The video seemed more focused on his view that there would be no more NATO if Trump is re-elected. I think he's embellishing a bit.
However, I don't think anyone can make any explicit guarantees that there won't be any foreign interference or other such shenanigans in US elections. Of course, the president can make sure there's an apparatus in place to detect and defend against such interference, but even that wouldn't be 100%.
The only way we can truly protect our electoral process is for the voting public to be more astute and vigilant.
We live in an open society which values freedom of expression, freedom of the press, and freedom of speech. As such, we have to expect that there will always be those out there who are trying to "interfere," in one form or another. And when it comes to politics, there will be a certain amount of mudslinging, fake news, pandering, dirty tricks - and all kinds of other BS that clogs up the airwaves and social media.
People get too caught up in the drama and lose sight of the issues. Considering the nature of social media and how things can go viral, it seems relatively easy for a few key individuals to stir things up and create a ruckus. If people didn't get so caught up in it and looked at things more logically and rationally, they wouldn't get so easily suckered - and it would be that much more difficult for any outside agency to "interfere."