The answer is nobody. Accounts regarding the 1812 War which lasted from June 18, 1812 to February 18, 1815 never mentioned any exact winner since there is no winner at all. There was a truce between the two opposing sides - the United States of America and the United Kingdom. However, for the perspectives of the Canadian, they won since their territory was not snatched by the US. On the other hand, Americans would say that it was a tie.
Yes, it is true that in general the Northeast was the region most opposed to the annexation of Texas, since this would have meant an expansion of Southern power, which many in the Northeast wanted to avoid.
