The difference in the US is that employment is mostly "at-will". An employee can be let go pretty much any day without notice.

So when you change job of your own initiative, it is assumed that you first get a new position, then give a notice and start your new position. If you have gaps, we can imagined that it's because you were let go (and therefore were unprepared to start something new). Now, why were you let go? Were you not performing well?

I'm not saying it's right or wrong; just explaining how long and recurrent gaps can be interpreted.