Yes, the US will allow any postage stamps to be used at their face value. Used stamps cannot be re-used, that would be illegal.
Not sure what you may have, as the US did not issue a Christmas Stamp in the year 2000.
The stamp has to be accepted where you mail the letter. If you are mailing in Canada, you need a Canadian stamp. If you are in the US mailing to Canada, you can use a US stamp.
44-Cent First Class : February 4th , 2011 .
the stamp act effects us today because it mad3e the war so their for if it would not have happened w wouldnt have had the war and todays life would not be the same
The first US stamps were issued in 1847. The 5 cent stamp with Benjamin Franklin can be purchased used for $715. Unused the stamp can be purchased for $4,500.
You can use US postage since origin US but since int'l will take more than 1 stamp
Yes, you can ... forever ...
No, you should only use US stamps for mail posted in the US.
Today (February 4, 2015) it is worth 80 cents US.
Yes, this stamp can still be used for four cents of postage. It was issued in 1991.
No, you use the postage of the country where you are mailing the item.
You use the postage of the country of origin, in this case, you would use Canadian postage.