Taking advantage of the fact that today is the 250th anniversary of the United States… I’m going to explain how to use the Maltese and US-MP civilizations in campaigns… if someone can make a mod to share it, that would be great, since this is something the devs failed to do, unlike in AoE 2, where they always add new DLC civilizations to the campaigns…
You could even do it with a mod or not, changing the campaign civilizations to your Maltese and multiplayer United States civilizations (although you would need to have both DLCs purchased and installed)… I know, but not everyone knows, that you can edit the official campaign itself. To do this, you need to copy and paste from the Campaign to the Scenario Editor, and if you want, you can save the edited version and overwrite the original version in the main game. Plus, I can use HC Card Desk from Skirmish.
To find the official Campaigns file. Let say for example Drive D, go to SteamLibrary>Steamapps>common>AoE3DE>Game>Campaign and you will find them along side with Historical Battles and Challenges. In case if you get confused on with “Wonders”, it’s The Asian Dynasties. Then Copy and paste the files into [Username]>Games>Age of Empires 3 DE>[Random Numbers]>Scenario and it’s done.
As for the HC Card Desk you use for Skirmish or online, go to [Username]>Games>Age of Empires 3 DE>[Random Numbers]>Savegame and you will see your Civ HC on there. Copy and paste them (XML) to SteamLibrary>Steamapps>common>AoE3DE>Game>Campaign into any existing files or make your own file like HC. Then renamed them for example: sp_Dutch_homecity.xml to Homecity_sp_Dutch.xml so it can use in civilization you choose to play as. Enjoy!