Filtering navigation links?

I'm creating a website for an event which is happening in two different locations. The client has requested that, if possible, the site includes UK and US links in the primary navigation, and for each of these I have a secondary navgiation including the relevant info for each of these events.

I'm wondering if it's possible to create secondary navs that appear based on the primary links – much like a language selection? eg.

UK > UK about, UK agenda, UK speakers, UK contacts
US > US about, US agenda, US speakers, US contacts

Worst case scenario, I think I will have to list this information in drop down pages. In this case, does anyone know if it would be possible to get the drop down pages to appear on click, rather than hover, in a bar that would appear beneath the primary nav bar at the top?

Thanks!

You can place all links on nav, then use CSS/JS to hide the corresponding items on each page.

JS would be better, but I think no one will answer here for free.
CSS, manually, will be easier, and you can place all on secondary nav, then share url, I can take a look with code to hide UK items on English Page an vice versa