We spend very little of our overall budget (less than 1%) on foreign aid, and that number is going to be cut further still this year amidst the economic troubles and budgetary debt crisis. Bangladesh receives a much smaller fraction of that foreign aid, only $172 million in 2009, for example. We spent nearly 4000 times more than that on US National Defense and 1100 times more on interest for our national debt. So such aid, while it can do much for poverty-stricken Bangladesh, truly has little to no impact on American pocketbooks or national debt load.
Another way to look at it is that, by comparison, we are a very wealthy country, even in bad economic times, and for us to shell out small amounts of aid to the developing world is simply the right thing to do in a humanitarian sense. To put it another way, we should use a small fraction of tax dollars helping countries like Bangladesh...because we can.