These are the bad things that would happen. Video games would never be the same. Nintendo owes its initial success almost completely to the American market. Without Nintendo doing so well, sony would have never been betrayed by nintendo and make their own console. So basically without America the current three video game giants would not exist. With the exception of nintendo, which may still be a very niche video game company in Japan. Cars today would probably be 30 years behind compared to the current ones. Humanity wouldn't have the ability to blow up the planet thirty times over. That sure sounds boring. British TV rather then American would probably be the most popular in the world. Soccer would be the only sport anyone could enjoy watching. I do love playing soccer, due to being born in Europe and all, but watching it is such a chore due to how absurdly common it has become for players to fake injuries and roll around for 60 seconds in hopes of getting a free kick. And worst of all fast food might not even exist...
As for the boring history and such. There is no telling what wars and inventions would have not happened or happened later without the United States, but assuming European conflicts happened in a similar order... WWI would have taken a bit longer. WW2 would have been vastly different. Assuming the united states never existed and ended up being a colony similar to canada in population size, Japan would have invaded Russia alongside Germany and probably conqured it. Germany would have conquered all of mainland Europe and the UK would have sued for peace. Japanese empire would end up including North America, Asia, and Austalia. Germany would have Europe and Africa. Eventually a cold war between the two empires would happen, and both end up collapsing because too many of their subjects want their independence.
