I did some reading up on the U-boat war in WWI. The primary issue that brought the USA into war with Germany (and Austria-Hungary) was the German submarine campaign. The Germans twice instituted "unrestricted" submarine warfare in WWI, since it was their best chance to defeat the UK. The UK could not survive without a steady flow of imports brought in by ships. So the Germans instituted unrestricted submarine warfare (meaning they released their U-boats to attack without warning and sink any merchant ship bringing supplies into the UK). This naturally endangered a certain number of American lives, and the USA was naturally not pleased about that. However, the Germans felt that it was worth the risk of provoking the USA, because it was the one and only practicable way they could decisively defeat the UK...and win the war.

They pursued this policy up until the sinking of the Lusitania in 1915. That sinking caused such a storm of anti-German feeling in the USA and such a propaganda windfall for the British that the Germans were compelled to stop their used of unrestricted submarine warfare for fear of bringing the USA into the war. They didn't stop the U-boat war entirely, of course, but they had to considerably restrict which ships they were targeting from that point on....and the damage to the UK economy was greatly reduced as a consequence, which defeated the purpose of the U-boat war from the German point of view.........so the overall effect was that the sinking of the Lusitania gave the British a lengthy respite from the worst effects of the German submarine campaign.

That situation endured until 1917, when the Germans decided to resume unrestricted submarine warfare in a last ditch attempt to starve out the UK and win the war. Even neutral ships were targeted if they were bringing supplies into the UK. Now, the Germans knew that this would inevitably bring the USA into the war, but they hoped to defeat England and France before the USA could bring its strength to bear (figure about 6 months for the Americans to effectively bring powerful forces into the western front). It was the last throw of the dice for the Germans, and it almost succeeded as their final offensive in the West nearly broke through to Paris...

...but the French and British managed to hold the line. And the USA was now in the war, having declared war on Germany. And that was that. The Germans had made their last great effort, nearly won out, but not quite good enough....and from that point on their defeat by attrition was inevitable.

It is perfectly understandable, under the circumstances, that the USA would have gone to war against Germany in 1917. It doesn't indicate that the Germans were any more to blame overall for WWI than anyone else was, but their submarine campaign was what brought the USA into that war. It's also perfectly understandable in a military sense why the Germans fought that submarine campaign. Like any nation, they were doing whatever they thought could secure them a victory, and using the practical means at hand.

Submarine warfare was a shocking new development at that time, because in previous wars blockades had always been accomplished by surface ships which were not usually required to sink foreign merchant ships...just to force their surrender, put a prize crew aboard, and take over that ship. Submarines had no room for either prize crews or prisoners, had to strike by stealth and sink merchant ships outright, often causing the death of much or most of the crew. This was shocking to people of the time, it was seen as a war crime by those affected, but it WAS the only effective way to use a submarine, so naturally that was what the Germans did (and so did everyone else who had submarines from that point on).

When a new technology re-writes the rules of war, people are usually pretty horrified about it. Some examples....

submarine warfare
aerial bombing of metropolitan areas
poison gas warfare
machine guns
tanks
atomic weapons

In WWI a number of new weapons were introduced and war became far more terrible than it had ever been before. People stumble inevitably and tragically into such developments, because our technological expertise is usually charging along way ahead of our grasp of morals, ethics, and our (leaders') willingness to forgo competition in favor of peace and accomodation.