Crown Store purchases aren't shared between the 6 megaservers. Only things that carry over are Crowns, Twitch Drops and Chapters (if you purchased them from the ESO website).
Each platform (PC, PS and XBOX) has access to 2 the regional megaservers (North American and European):
PC-EU
PC-NA
PS-EU
PS-NA
XBOX-EU
XBOX-NA
Like I said, all Crown Store purchases remain on the server you made the transaction in. If you want to play the Clockwork City DLC on both PC megaservers, then the best option for you is to have an active ESO+ subscription. And I'd also suggest buying any DLCs on the server you tend spend more time on.
All crown store purchases are server specific, including things that are applied to both servers if you buy them outside the crown store. For example if you buy Necrom now through the website you'll have it on both EU and NA, if you buy it in the crown store after Gold Road is released it will only be on the server you're logged into at the time.
PC EU player | She/her/hers | PAWS (Positively Against Wrip-off Stuff) - Say No to Crown Crates!
"Remember in this game we call life that no one said it's fair"
If you buy a stack of tri-pots with gold on PC-EU, you do not get a stack of tri-pots on PC-NA. The game does not care if it is crowns, gold, tel var, voucher writs, or whatever. Those are all in-game currencies and stuff bought with in-game currencies stays on the server where you bought it. Only items acquired outside the game (such as crowns, ESO+, Chapter purchases, etc.) are shared.
I am not crazy about this design. But that is the logic. The cash you bought crowns with is real currency, but the crowns themselves are just another in-game currency.