I'm in Canada and shipped my failed video card back to EVGA for a replacement. I followed all the directions. I put my card in an anti-static sleeve and then put packaging material all around (at least two inches worth on all sides) and shipped it in a very sturdy box.
 
At the moment, however, it's being held by US Customs for some unknown reason. 
 
My question is: if US Customs decided to open the package and then doesn't repackage it properly, will EVGA refuse the card? 

Your package is most likely fine. Customs tends to pull every so many shipments to go through them more finely and your package probably just got caught up in that. They very rarely actually open a package unless its showing weird results on the machines and the dogs are hitting weird on it too. Heres the info to cover damage by them but being your Canadian im not sure how that would work on your side, so you may have to dig deeper to find out.
 
https://help.cbp.gov/app/answers/detail/a_id/178/~/tort-claims---claim-for-property-damage-or-loss%2C-or-personal-injury%2C-or-death  
 
On a side not...... Maniac!! Where the heck have you been man?!?!? Nice to see ya lurking again.