For better or for worse, the United States has been described as the self-appointed police force of the world by politicians and pundits alike. Like any good police force, the US has plenty of stations to dispatch officers from. Only, in this case, those stations are all over the globe and known as overseas American military bases.
It’s become accepted that there are US military bases around the world, but rarely does one stop to ask exactly how the US even has military bases in other countries in the first place. The story is a mixture of diplomatic relationships, international alliances, and good ol' fashioned American military dominance.
The historical reasons for US military bases abroad are as varied as the bases themselves. Sometimes, the US is helping an ally out with training and defense. Other times, they’re keeping an eye on a recently defeated enemy. Bizarrely, they sometimes even hold their worst political enemies in an illegal detention facility in a country they have next to no diplomatic ties to. The basic rule of thumb is this: if the US could benefit from having a military base in a certain location, they’ve probably already got one there.
The most obvious and direct incentive to host a foreign power's military base in your country is some sort of financial payoff. Countries like the US can pay other nations for the privilege of having bases on their soil, something many of those countries then pay back by purchasing American military equipment.
The US has countless financial arrangements with other countries like this, and America's sheer power means that some of the neediest countries even pay the US to maintain a base.
Another major reason that a country may choose to host a foreign military base, American or otherwise, is to improve diplomatic relations. Such a move demonstrates a friendly relationship between two nations, and strengthens any pre-existing military alliances.
Letting the Americans host a military base in your country may yield future beneficial trade deals, for instance. Having the Americans open up shop in your country sends a clear message to your neighbors that you’re friends with the USA, a position that has generally been positive from a security standpoint.
Of course, perhaps the largest incentive to host an American military base in your country is the additional national defense and security it provides. Just having American soldiers on site is going to provide instant stability to an area, both through their expertise and the sheer force of the army they represent.
It also provides the host country with a visible and effective demonstration of their military alliance with, and protection from, the United States. People don’t mind America being an international bully when said bully is on their side.
When a country finally rears up and demands that Americans remove their military bases, the answer is still usually no. This is because the US wields an unbalanced amount of power within the United Nations, meaning that the UN will almost always back up America’s claims.
This became apparent when Cuba attempted to have Guantanamo Bay returned to their control after the US turned it into a brutal detention facility. The UN simply said “no,” and that was that.