KL gateways in the US are at the moment:

JFK ( one late flight on 23456 )
IAH
SFO
LAX
DTW ( NW 53 changed to KL 617 5 days ago )
MEM
MIA ( NW metal right now, will be operated by KL from September )
ORD ( make sure to ask for ORD, first !! More a Cargo flight for KL operated by 747 Combi, normally lots of availability in coach )

Canada:
YUL
YYZ
YVR

Perhaps you can get seats via Canada !!

Good luck !!