I think it's a great idea, or it WAS at least... more than a century ago!
I've long been of the opinion that the US should have annexed the entire former No. American Spanish colonies (not merely Fla, Tex, N.Mex, AZ and Cal.) all the way to the Isthmus during the 19th century when the rest was absorbed.
That would clear up any confusion regarding sovereignty over the canal as well.
When the 54/40' border dispute with Canada occured at the boundry with BC (if not sooner during other differences) the US should have given Great Britain a reasonable, closed-end time frame to extract themselves, their own tangible possessions and presence, from the continent or face being pushed into the No. Atlantic.
Unfortunately I don't see how present day mimicry of a one nation No. American continent serves any purpose other than creating even greater security and social problems than those already facing us.