True, radar was lacking in the German U-boots. However, comparing the Atlantic Ocean to the Pacific, you'll see that the Atlantic would be **Slightly** easier to patrol, especially as in earlier in the war the U-Boots were patrolling off of the British Isles only and could rely on sightings for FW 200?? Condor search planes from the mainland.
So Radar really came handy to the Americans because they had a lot more area to search and could not rely on visual sightings of convoys from land based aircraft until later on in the war.
Please shove this post back in my face if you see any faults in it
I am NOT an expert but am recalling only vague memories of some reading on the Pacific Campagins as well as the Atlantic.
With Regards,
Krauter