Canadian Bank Note Company printed two US stamps (Scott 2184 and 2186),
actually as a sub contractor for Stamp Ventures.
See here from the 2008 Scott Specialized.

I remember there was a big outcry as to why the USPS was using
a foreign printer.
Similar to Ashton Potter who originally was a Canadian security
printer but was finally given a USPS contract after a name
change to Ashton Potter (USA) and relocating the plant to upstate
New York.