Pelosi was not trying to change U.S. policy but the 47 are.
Yes, actually, she did. She made it clear that the United States is weak, because the leadership is divided, and whatever image President Bush attempted to put forward, she single-handedly destroyed, because it was more important to play politics and make Bush look bad than to do what was right to make the United States strong in the eyes of its enemies.
And the last sentence is bogus because if there's a constitutional issue, the Pubs could have taken it to the SCOTUS and the court could fast-track a decision. And exactly what do you believe Obama is doing that's supposedly unconstitutional on this anyway?
I'm not going to go through everything that President Obama has done wrong and gone against the Constitution.
However, Congress was clearly moved at what Netanyahu had to say when he addressed them. The idea that it is bad for the free world for Iran to have nuclear capabilities was made very clear. I'm not sure what Obama is playing at, but he knew that what he is doing with setting up a ten-year time limit is against the will of the Congress.
What Obama did may not have expressly violated the Constitution (this time), but it is clear that he isn't interested in doing what is good for the country, again, so that he can play politics.
The 47 people made clear that Obama doesn't have the right or the consent to do what he's doing. Obama seems to have forgotten that there are three branches of government, and the one that holds the power to declare war or make sanctions is the one he is set on ignoring because they are the wrong party for his tastes.