The answer is yes, The Americans are a zealous people when it comes to defending their country but even they would recognize that sending ships filled with ammunition ,that you know is going to be used against the Germans, is going to provoke the Germans in attacking your ships.
Which is irrelevant. Germany resorted to unrestricted submarine war precisely because it could not practice restricted war, which would oblige it to inspect ships and determine that they carrying war materials before they could be sunk. It would also make them responsible for sparing the lives of the crew and bringing them to shore somewhere. This was a practical impossibility for the Kriegsmarine and was never attempted.
There wasn't even any guarantee that the US would accept it, even if they tried it.
Either way, to attempt to present this as a German response to US support is to completely reverse the sequence of events. Unrestricted sub war committed them to sinking neutral shipping regardless of what cargo they were carrying. And they did this before any kind of aid was offered by the US.
But even so unrestricted submarine warfare wasn't the only option. They could have easily go for aerial supremacy and bomb the ports and industry or mine the ports. And if my focus was the British i would send the whermacht to north Africa. if they could capture the Egypt and Morocco the British empire would be cut in half while while having access to the oil of saudi araby.
They DID go for aerial supremacy, in the Battle of Britain, and lost. And as I pointed out above, modern thinking is they had no chance of winning. They did bomb ports and industry, or tried to, and they certainly dropped mines. But the British were quite capable of dealing with these things.
Losing Egypt, and I presume you allude to the Suez canal, would have made life more difficult, but far from impossible. Plenty of shipping even today goes the long route around the South African Cape, for precisely which reason U-boats operated in those waters too. It would not have cute the Empire in half; it would have simply lengthened supply lines.
And those armies you want to transport to Africa, and the oil you want to ship back? They have to go by sea, across the Mediterranean. The only reason that British did not deploy in the Med in any great strength is because they were instead blockading the German surface fleet in the Baltic. If Germany had genuinely managed to cause significant trouble in North Africa, the British could easily have shut it down and blockaded the Italian coast. This would have let the Tirpitz etc. out, which would have been bad, but not as bad the alternative. On top of this, whatever forces had shipped to North Africa would now be trapped.
It's a mad plan and there are good reasons it didn't happen.
And do not forget that British empire in 1941-2 was facing a 2 front war with the Japanese attacking their colonies.
Britain had plenty of experience being a naval empire. It has a historically small army precisely because it could afford to fight small, localised engagements in areas that can only be reached by sea. This also entails knowing you can't necessarily win every fight, but that you can dominate in the long run.
I would also suggest you read that part. their was a very strong antiwar movement in the america's during both world wars.
I'm well aware of it. I've mentioned myself that declaring war on the US was an act of hubris because every day that Germany could avoid bringing the US into the war was to their benefit. But every anti-war movement struggles when civilians are being killed, and that is precisely what unrestricted sub war was specifically going to do.
And more generally, look where you are now? In order to defeat the British, you're now trying to neutralise America. Every attempt to solve the problem creates an even bigger problem; Germany keeps snowballing the war into a bigger and bigger catastrophe, precisely the opposite of what was required for the only kind of war it could reasonably expect to win.