Congress is the only government body that can

Congress is the only government body that can actually declare war. They only  hold the sole power to declare war. For the United States, Article One, Section Eight of the Constitution says "Congress shall have power to ... declare War". Hope this answers the question.

John Tyler assumed the presidency of the US when President William Henry Harrison died. On the last days of his presidency, Congress passed the joint resolution to annex Texas, the Republic of Texas voted to accept the annexation on June 23rd. On March 1st, the last day of his presidency, President Tyler signed the Joint Resolution for Texas Annexation.