If you arrive in Canada with a work permit, you can say something like that. If you arrive as a visitor planning on looking for a job, they may turn you back at the border if you say that.
I am sure the US would do the same to a Canadian. If you arrive as a visitor, you should be visiting. There are no rules against looking for a job and arranging a work permit once you are in but if you announce it at the border, they don't have to let you in as your intention is something other than a visit.
Open work permits aren't just handed out like candy you know. One of the exceptions is the swap program and working holiday visas that various countries are parties to. Swap is limited to students though. There is no other working holiday visa I know of for US citizens. Various other countries, like Australia and some European countries have working holiday agreements with Canada where you don't have to be a student and can get up to a 2 year open work permit.