Cuba was indeed once a rich country. Sanctions and communism came at more or less the same time, which may be why you are misjudging the effects of both. The reason Cuba is poor is because of communism. Period. US sanctions and any problems with their "factories" are by far secondary factors. Communism (and other forms of totalitarianism) makes and keeps countries poor. Trade sanctions are only effective at crippling a country's economy if the whole industrialized world joins an embargo. Otherwise there are to many ways around it. Both of these points have been proven time and time again in recent history.
If Holland were to loose the US as a export destination......
I don't know the way it is with Holland, there are certainly special cases out there. But I don't think many countries the size of Holland are out to buy votes in the UN like the US, Russia and France often have to do. Nor is the US a member of a trade block like the EU. Though we are trying...with NAFTA.
Also keep in mind that the US is not a monolith. The US as a whole may not have much to lose from losing Holland's trade, but many individual Americans would and they would lobby like heck in congress and other places to get the US to go easy. I don't know if this has happened to Holland but it has happened time and time again in US negotiations with countries like Japan. This is even though Japan has a huge trade surplus with the United States.
Our political system makes it easy for special interests and even foreign contributors to weaken our stance in trade negotiations.
Since most of the trade wars are between the US and the EU,
patently false. At least in the US, most domestic political debate about trade is about trade with poorer countries. Some of the most contentious trade negotiations the US has ever had have been with poor countries like Mexico and China (yes, China is still mostly poor).
The EU is not going to stop the war-on-terror, war-on-drugs and the war-on-illegal-arms (who makes up these names!). The EU has too much to loose when they stop it.
The EU is indeed not going to stop the war on terror, drugs, etc. But there are various degrees of cooperation and participation. It is not a "You are with us or you are not" sort of thing. Even friendly Nation states often do not like to share intelligence information, let military and intelligence opps be conducted from their shores, etc. Often police and intelligence agencies, banks, etc. all want to protect their own turf more than they want to advance the overall cause. It can take A LOT of influence from the politicians to get these folks to work together even with other corporations or agencies in the same country, let alone with foreigners. The degree of cooperation offered is very important to the US and is an important bargaining chip a state can offer at trade negotiations. It is a bargaining chip that the US usually doesn't have when dealing with other states - though there may be a few exceptions.
poorer countries. Countries that tend to be dependent on the US for trade/protection/aid anyway. They are not going to piss of the US over trade.
They have done so many times. We have had all sorts of trade disputes with poorer countries we have a military presence in. Asian countries in particular. Their need for our protection sometimes makes them more reluctant to kick us out but that is about it. We almost always need their bases, etc. more than they need our protection. And most of them would rather have us somewhere else in the region than on their soil if possible. No nation really likes to have foreign troops on their soil long term. Even the Philippines kicked us out of Subic bay, etc.
One rather open secret is that many of these bases may be more of a danger to the country they are in than they are a protection. They can be a target for terrorists or involve a country in any war that the US may happen to be involved in nearby. The defense plan for many overseas military installations is simple evacuation in the case of any significant attack, with plans to "re-invade" later. This is not a plan that inspires a host country's confidence. Many times, we have to offer economic inducements in the form of aid or trade privileges to get countries to let us stay.
As for American aid, European and Asian industrialized countries give aid as well. In fact, they often give more in proportion to their economic size than America does. In terms of aid influencing trade: America has the advantage of being able to give more in absolute dollars due to its size, Europe has the advantage of not being able to worry about other issues as much. Sometimes, trade privileges are given as a kind of aid. So the whole issue seems to be kind of a wash.
As a parting thought, I wish the US would spend more on foreign aid. What we spend now is not nearly enough given the size of our economy and what other rich countries give. Those who say we should tackle domestic poverty first should take a trip out to Somalia or someplace like it and go see how good even poor Americans have it compared to many other places. We should be careful in how we spend it, and not let people get to dependent. However, we should also not let past mistakes be an excuse not to act. Aid now is much cheaper than military action later anyway.