I know that many thousands of German and Italian WWII POWs were transported from Europe and Africa to the United States by ship. I was wondering, were any of them killed during the transport from attacks by German u-boats?
Hard to say never ever but apparently no major incidents like that. The Allies generally used the same fast ships ships for transatlantic personnel transport either way, either too fast for subs to have a high probability of sinking them even unescorted, or with escorts if near the lower limit of speed for independent sailing (~15kts usually). No ships carrying a significant number of US troops from US to Europe* were sunk enroute with any troop losses, in either WW. It’s not shocking if no similar ships happened to be sunk going the other way with prisoners, especially since transport of Axis prisoners to the US was only in numbers from mid 1943 after virtually the whole Axis force in North Africa was captured, by which time Allied antisubmarine forces had German subs under heavy pressure.
The British liner Empress of Canada was sunk in March 1943 in the Atlantic off Liberia by the Italian sub Leonardo da Vinci killing among others a few 100 Italian prisoners being transported from South Africa to the UK (planning to send them eventually to the US? not clear from any source I know).
*the transport Dorchester was sunk by U-223 with heavy loss of life in 1943 carrying US military personnel to Greenland, Leopoldville by U-486 in the English Channel in 1944 carrying US troops to the Continent from UK, the worst was Rohna sunk by German guided bombs in 1943 carrying US troops from Algeria>Italy. No US soldiers at all were lost in troopship sinkings by submarines on their way to France in WWI.
Just today i watched a clip about a POW who escaped and lived as an American for nearly 40 years. It was very cool.
There’s a list of all ships hit (not just sunk) by German U-boats by month here if someone were really motivated.
There’s a point even without that effort. Totals of ships hit by year for the course of the war:
- 1939 - 165 ships
- 1940 - 563 ships
- 1941 - 501 ships
- 1942 - 1322 ships
- 1943 - 582 ships
- 1944 - 243 ships
- 1945 - 98 ships in the 5 months before surrender
US ground forces entered into combat with Germany and it’s allies in November of 1942 with Operation Torch. German forces in Tunisia surrendered in May 1943 meaning a big spike in prisoners to be handled. By that point, the U-boat campaign had largely faded from its peak in 1942. Only July of 43 saw more than 50 ships hit after the Tunisian surrender. 208 of the ships hit in 1943 were June or later for an average of 29 a month even with July’s peak.
As Corry El pointed out the threat had receded quite a bit before the US was handling large numbers of prisoners.
Just by the way, in 1945 an American soldier went nuts in Utah and massacred prisoners.
8 July 1945 Salina UT 9 killed (shot) (Utah prisoner of war massacre - Wikipedia)
I just watched that as well; that’s what inspired my question. 
It also happened that Allied POWs of the Japanese died on ships sunk by Allied action, my father’s cousin among them.
The US bombed Italian POWs torpedoed and rescued by a U boat.
Note that the prime target of wolf packs would be ships heading to Europe. Those ships had supplies and troops. More valuable than the ones returning. So ships returning from Europe were more like targets of opportunity.
Which was then attacked by Allied aircraft, twice, despite flying a Red Cross flag, killing more survivors. One of the most embarrassing war crimes of WWII.
The U boat commander radioed that he would not attack if Allied ships would come take the survivors and was attacked by a B-24. After that U boats were instructed not to rescue survivors.
That was true to some degree but again troopships were rarely sunk by German subs in the open Atlantic, going either way. Without specific code breaking intelligence (like US subs often had against high speed Japanese targets) subs were unlikely to get good firing positions against ships in upper teens kts speed or above transiting the open ocean, even sailing independently without escorts, and ships at the lower end of troopship speed around 15kts were often sent in particularly heavily defended convoys. Against major surface warships, subs might know the warships would be milling around a particular operational area even if going fast. And German subs managed to sink 4 US troopships in the Nov 1942 invasion of Morocco, but after they disembarked their troops, by penetrating a defended anchorage.
The results of 1,000’s of German sub attacks on ships in both WW’s bear this out. German subs sank almost no troopships transiting the open Atlantic in either WW (the three biggest WWII exceptions of ships sunk with heavy loss of US ground troops given above, only one in the relatively open Atlantic, en route to Greenland). And we know this wasn’t for lack of strong capability by German subs, nor overwhelming Allied ASW capability except in the last couple of years of WWII…which was also when most Axis POW’s were transported to the US.