Help understanding - Combining Multiple Identical SQL Database, data models

[Jamie_Macca]

Hello I'm looking to combing 3 SQL Databases in Power BI. The 3 databases are Identical in structure but are for different regions, UK, EU and USA. These are large databases that manage Customer Details and Orders for each region. 

All columns and relationships are the same in each database but the system references/UIDs will be dupilcated as ID 1 in UK will be in use by a different Customer ID 1 In the USA, I want to be able to report on all databases e.g. Customer tables and orders tables over all 3 databases combining the data from each in visualisiations for Dashboards.

Is there a way to combine all this data into one Data model but still be able to tell which Database the data has come from (have a unique database reference UK1 EU1 USA1 for each table in the database)?

What is the easiest way to combine these databases? I've looked at the Append and Merge functions but am stuggling with the size of the databases. 

There are a nubmber of matching tables around 10 for each database that have identical Column names and relationships.

Any help or guidance would be greatly appriciated.

[Jamie_Macca]

Is there anyway to do this or will the conflicting (duplicated use of) system Ids make it too difficult?