Okay, we get threads all the time on this board that ask the same basic questions: "What if America conquered all of the Western Hemisphere", or "What if the US participated in the Scramble for Africa", or "AH Challenge: Give America territory in Europe, or the Middle East, or up my ass...".
Well, as most experienced AH.commers know, America had many reasons that either, A) they couldn't expand more than in OTL, or B) they didn't want to. Let's look at the reasons.
1. Canada- unless all of British North America secedes during the Revolution, chances of conquering of annexing all parts of what's today Canada are small. History would have to take a decidedly different course. I mean, in OTL we were lucky enough to get Washington state.
2. Mexico- yes, we could've annexed all of Mexico if we wanted to, but the thing is, we didn't. Throughout most of America's history, the US have been more or less openly racist. Incorporating all those dirty brown-skinned, Catholic, Spanish-speakers would be just horrible. Notice the areas we actually annexed was largely uninhabited.
3. With regards to the two previous subjects, throwing British intervention away from the Canada issue and residual racism from the Mexican one, pre-1865 taking too much territory to the north or south would throw off the delicate balance of free-state/slave-state. Notice why Texas was only admitted as one state, despite it's size. I mean, there was considerable opposition to the Mexican-American War from the north. Now imagine if the north had included the Maritimes, Quebec, and the Ottowa penisula. The resistance would be multiplied.
4. After the Civil War, we still have problems. As the years pass, we have less and less reason to want to declare war on Britain (except for the years immediately after the war, too be fair), we were just doing too much trade with them. On Mexico, why would we want to annex the whole of the country? Racism was still at play, and even throwing that aside, do you honestly not see that making Britain/France angry. With the Carribean, well I can see Cuba and the whole of the island of Hispaniola being annexed without a huge stray from real history, but that's about it.
5. Now grabbing territories all over the world... just no. Not gonna happen. Yes, I know, the Phillipines were annexed, but they were never intended for statehood. We just held them long enough to "civilize and democratize" them. In fact, they probably would have gained independence earlier if it wasn't for Japanese aggression. And don't even bring up Liberia. It's entire reason for existence was to get blacks OUT of the US. Incorporating it into the Union would defeat the purpose!
Okay, now that we've gone over all this, what WOULD make America more expansionist? What social, cultural, political, whatever changes at one point would make America willing to annex the Western Hempisphere, participate in the Scramble for Africa, obtain territories in Europe, the Middle East, up my ass, etc? Any PODs at any point in history are acceptable. And yes, DoD would be a great example of this, but let's think of original ideas. Any takers?