No, it can't have been done with projectors because when the Canadian anthem was playing and there was a great big Canadian flag covering the entire ice surface, I didn't see the Tampa Bay Lightning logo that's clearly visible in the middle of the arena ice when the flags weren't there.

So, I can see how a projector could produce a Canadian or American flag onto the entire ice surface, but how does ADDING light remove the logo and the 4 face off red dots and circles?

The only thing that makes sense to me is that the flag was put into the TV signal so that the people in the arena couldn't see it, and the people at home could see nothing but the flag.

If those flags were done by projecting light onto the ice, the Tampa Bay Lightning logo would still be visible to everyone in the arena and everyone watching at home. And, in the case of the Canadian flag, that would muck up the appearance of the Canadian flag by messing up it's central red maple leaf. And I recall clearly that it was a normal Canadian flag, with no hockey team logo messing up the red maple leaf, and no face off dots and circles messing up the red bands on either side of the maple leaf.