Mixed date formats

Hello,

I haven't found the answer I need within previous questions.

My pc is set to European date format dd/mm/yyyy.  A lot of my data is in US format mm/dd/yyyy.  I did find the setting to change Type and Locale within Power Query Editor. Having applied that though it is giving me errors on saving.   When I had managed to save that change with a subset of the data, my issue was when using the DateDiff function, Today was still being seen as European format.  I came across the previously given advice to use the Format fuction to change Today to US format.  I cannot however figure out where to use that though so that it impacts my DateDiff column correctly.   Would appreciate your guidance