Haven't seen any official details yet so just speculating at this point, but the China travel ban applies to "any foreign national who was in China during the last 14 days" (except green card holders/diplomats). It'll likely be a similar definition with the EU.

Edit: https://www.dhs.gov/news/2020/03/11/homeland-security-acting... confirmed this (countries in Schengen area)

This is possible. But less likely.

The point of travel restrictions is not to be 100% effective, but instead to reduce the number that travel.

Chunnel notwithstanding, Northern Ireland is part of the UK.

You can walk from France to the UK through the Chunnel, technically.

Yes, its dangerous and illegal but it's been done!

https://www.theguardian.com/uk-news/2016/jun/22/sudanese-ref...

that's a 26km tunnel frequented by bullet trains, take some water and a helmet.

The UK is in Europe.

Politically, it's not in the EU, but geographically/physically it's still in Europe.

Geographically Russia is in Europe

You're thinking of the European Union. Europe is a geographic area. The UK is still in it.