One of the first and most obvious differences is that the committees in congress have the ability to stop a proposed bill before it has even reached the floor of the reps or the senate. This shows immense power as effectively the committees in congress have more power than individual senators or representatives themselves.
To further emphasize this point one only has to consider that in 1996, 6,808 bills were proposed and only 337 of them were implemented. This is quite a contrast as it is much easier for a bill to be passed in England, even with the oversight of the house of lords due to the massive majority being enjoyed by the Labour party at the moment. However congress can re-introduce a bill if it has been amended, although once again it has to go through the lottery of the committees.
This is also quite the opposite of committees in the house of commons as these committees don't even get to be involved if a bill is considered to be of constitutional importance as these sorts of bills are debated on the floor of the commons.
The most a standing committee can do is amend a bill after its second reading in the house of commons. Amenments however are limited as the government usually curtails the amount of time given to a standing committee to consider the bill and therefore keep the number of significant changes to a minimum. This is a process known as 'the application of Guillotine.' The committees in congress also have amending powers, particularly when it comes to final stages of bill being passed as a bill has to pass in identical form through the house of Reps and the Senate for it to become law. This means compromise must be reached and this...