Because the U.S. can afford it, being the wealthiest nation on earth, and should therefore take on its share of the burden. Also, because the U.S. can do good, and give these people liberty and safety; if they don't deserve it, why do you?
Yes, absolutely. Most mature people do and most modern societies do. The U.S. has actively supported freedom and democracy around the world since it became a major power, and part of its ethos has been to take in the 'hungry, tired and poor'.
In fact, if you are an American, you are one of the major beneficiaries of this attitude: The entire society, it's freedom, safety, and prosperity, is build on sacrifices of others. Like everyone else alive today, it was given to you by the generations before you. What will we give to others? Recent generations won WWII, gave the nation civil rights for women and minorities, and did so much more. What will we give to the next generation? Hatred and greed?
I also give money and food directly to the needy, and also to organizations who provide for them (they have far more expertise and resources than I do). Several of those organizations are governments, and I advocate for higher taxes in order to provide more of these services.
To truly believe that these actions are somehow extraordinary is to be naive about how the world really works. This is the norm of how communities function; if I didn't do my part, I would be looked down on and rightly so - I would be a parasite on everyone else. Who do you think takes care of your needs - food, shelter, education, healthcare, the arts, solving community challenges and problems, and much more? Some of it you pay for, and without a doubt some was paid for and worked hard on by people of good will (and some enlightened self interest). That hospital you went to is funded to a great extent by donations and tax dollars, for example. If you live in a democracy, it's up to the people to provide these things - they won't just happen for you.
Charity is also provided by government via tax dollars, something else the U.S. has always done and will continue, even under Trump.
This particular comment crossed into personal attack, too. That's bad. We ban accounts that do that, so please don't do it again.