Dependent Drop down list with DEPENDENT DEFAULT VALUE

Hello, all
It must be pretty simple to do it but I'm lost..

Situation:
I have two drop down lists 1) Country and 2) States/province

Country has list: [US, Canada]

If "US" is selected, [Arizona ,Florida, NewYork] is listed in the 2nd drop down list
If "Canada" is selected, [Alberta, Ontario, Quebec] is listed in the 2nd drop down list

Scenario:
First, I select "US" and choose the states to "Florida"
Next I change the country to "Canada" and forgot to choose province
Then, the 2nd dropdown list is changed to [Alberta, Ontario, Quebec],
BUT the current value is still "Florida"

Probem:
Now I have "Canada" and "Florida" selected in the sheet

Question:
If the primary list is changed, can I make the 2nd drop down list to show a default value (e.g. blank or the first entry i.e. Alberta)?
Could someone help? I have a serious problem with this issue. Example EXCEL file is attached below

Thanks in advance