The following is a paragraph from Brothers in Battle, Best of Friends (which is excellent, and has a very moving forward by Tom Hanks). It is from William Guarnere's perspective regarding being led by Montgomery:

What worried me was the entire mission was under British command. It was strictly a limey deal, under Montgomery. The Brits were different fighters than us. We figured that out real fast in Normandy. They were fighting the war for years and were tired of war. The soldiers were lions--they fought like the Americans--but they were led by a bunch of damned donkeys. Ever hear that said? The ranks were handed down, like with British royalty. They weren't earned. So who knows what was leading their army. See, now I'm educating ya! Their leaders were very leisurely in their way of fighting. They liked to stop for tea and crumpets and set up housekeeping in the middle of a battle. True. Tea and crumpets. I saw it for myself.

Later in the book, Bill returns to this thought:

Now, we never fought with the British in the war. They were supposed to come up and meet us in Eindhoven. The British were good soldiers. They had a lot of time in combat. But their leaders had them stopping for friggin' tea in every town. Maybe if they met their own troops in Eindhoven, not us, they would have fought better, instead of throwing two different armies together. That was a risk.

Now how much this was actually true could be answered by someone more qualified, but it seems it may have at least been a popular stereotype at the time, affecting American attitudes towards British leadership.

Was this historically accurate? I only remember reading that the argument was resources going to Montgomery in the north rather than Patton further south.