I just added a few new links to to my top navigation bar, but when I check the site on smaller screens some of the links drop down, splitting the nav bar into (2) rows. I've done this several times in the past as well, and haven't come up with a remedy.

On large screens all of the links align to the left and there is alot of empty space to the right. This is actually fine, but I would like to add more links to the top nav bar without it splitting into two rows on smaller screens.
www.usafleetsupply.com

How can I make this happen?