The prepared mustards, sold by the food giants of the Americas,
(McCormick, inter alia), make mustards I believe to be similar in
taste to mustards sold north of the border.

I have never seen a Mexican "Country Style" mustard. Or any variation
that would suggest Mexican-ness in a mustard. Sorry.

Yet:

The following website:

http://www.mustardmuseum.com/

would be another place to ask.