Edit width of submenu drop down

I have done quite a bit of css customization to the header, but I have one edit that I can't find the selector for. I need to make the drop down menu for standard menu (not mega-menu) wide. Currently, if you click on Cause Mapping (the first main menu item) you'll get a drop down. But the items in that drop down menu each take up 2 lines of text. I want to widen the dropdown menu enough for all submenu items to only take up on line.

What css do I need accomplish this?

Or is there a theme option somewhere that I missed?

Thanks,

Rob