A TPP without the US is of questionable utility as each of the proposed participants, aside from the US, factored in their proposed relationship with the US when agreeing to terms with the other parties.  Thus, without the US the relationship of each to the others is unbalanced to a greater or lesser extent.

In essence, this would mean that extensive (and long) renegotiations would have to precede a minus US TPP.

Bilateral agreements, therefore, make a lot of sense, especially between Canada and Japan.