I have changed my country from USA to Canada this morning and I have lost all my songs in library could you please let me know how can I get my playlists back and even my subscriptions too

You should review this information: https://support.apple.com/en-us/HT201389

Purchases and subscriptions are region based and as such Apple Music tracks and playlists will disappear when you cancel it to change regions.

Downloaded purchases should not disappear, But un-downloaded items may no longer be available in the new country’s store and should be downloaded before changing countries.

Any purchases that are available in the new country’s store can be re-downloaded.

Apple Music subscription service tracks and playlists will need to be re-acquired form the new region’s Apple Music catalog.

Your other subscriptions will need to be restarted in the new region manually like you did the first time. They won’t magically reappear since you had to cancel them before changing the region.

What a fatuous response. Someone has lost all of their music after changing regions and you direct them to a page teaching them how to change regions, with nought a single word addressing the issue?

Fifth bullet point under what to do addresses the issue. Download all of your stuff as it may not be available in your new region.