The American tanks "lent-leased" to Britain were so hopelessly outclassed by the German tanks that they were virtually death traps. However, the American, in their arrogance ignored the British requests for up-gunned and up-armoured tanks and went to war with the same models.
During the American landings in North Africa, the Afrika Korp shot up so many American tanks that there were wild exaggerations of the German strength to "explain" away their failure. The Americans were only saved by their possession of masses of artillery !! German tanks used to sit out of range of the American tanks and pot them one by one while the American tank ammo would bounce off the German tanks like peas !! The Grant and Sherman tanks could barely match the Panzer III which were already obsolete. They were out-classed by the Panzer !V which were being phased out and they were hopelessly out-classed by the Panther just coming into operation by then !!
The good thing from the Lend-Lease were the destroyers used in the Atlantic convoy battles !! Those were desperately needed and they did a sterling job fighting the U-boats !!
And, *NO*, U-571 did *NOT* capture the enigma machine that broke the German codes, no matter what Hollywood says !! Those codes were broken at Bletchley Park using a very early form of computing (IT angle !!) .