You're going to get a LOT of reductive and low effort answers from Lemmy radicals. But this is a super complex question, and there's not a 5-second ELI5 answer if you really want to understand.
Also, when the radicals scream at you, there's going to be a core of truth. They're going to yell about colonization and empires. That's a major factor, but not an exclusive one. However, for getting radical and rabidly furious its all they'll bother posting to you.
Things to investigate, because answering this for yourself in a meaningful way is going to take a while and require study. Here are some topics but NOT an exhaustive list:
Colonization
Resources (natural and otherwise)
Schooling, education, etc.
Stability, politically and otherwise (note this will have overlap with colonial and non-colonial powers destabilizing things intentionally for geopolitical gain)
Medicine as regionally practiced, traditional vs based on the the scientific method.
Geopolitics (isolationism, etc)
Geography (i.e. the US's greatest asset is its location, it neighbors no enemies and its main enemies are separated by an ocean. One of the key reasons the US focuses on the ability to project force)
Religion
Corruption (politically and non politically)
Crime and non-military/nation based violence (also could get grouped under personal safety and security)
And again, honestly, a lot of these topics will overlap, but that's what I mean by there isn't a quick, easy answer.
And the reductive stupid answer is just yelling colonialism.
There's a reason people get PhDs in this subject. It's not a quick, easy question.
Actually, you're just reducing complex issue of exercising power over other countries to "colonialism" than trying to criticize people correctly recognizing this issue as "radicals". Most of what you listed can be directly linked to western countries destabilizing other regions by military or covert actions, installing puppet governments, using their influence to steal resources and keeping other economies in check so that they don't develop into competitors. No one thinks that it's all because some country was a colony 200 years ago. Western influence never really ended in most of those countries and that's what is keeping them down.
And the reductive stupid answer is just yelling colonialism.
Most of those reasons, that are very real, are explicitly derived of colonialism.
For instance:
2 (resources) is the cause that the US promotes puppet right-wing governments or directly destroys countries to pillage them.
3 (education) is systematically destroyed in many countries because they want to make public education disappear so it's for profit. Again, following the US model and most likely benefiting US companies (for instance "educational" campaigns to teach proprietary products created by US companies, e.g. Microsoft)
4 (stability) is directly threatened by the US foreign policy of destroying every country that is ideologically or economically inconvenient for the unimpeded proliferation of unbridled, savage capitalism.
6: in many developing countries public health has been destroyed to follow for-profit schemes based in the US model, to benefit either US companies or US-backed right-wing politicians.
11: Crime is worst in countries reduces to poverty, in many cases by US-backed lending policies sending countries into misery.
All this, of course, is supported by years of colonial teachings after which the people in the "developing" countries despise themselves and look up to the powerful countries as inherently superior, even morally.
Not just the US. Cambridge Analytica is trying to manipulate our politics through scummy means such as misinformation campaigns. And our country is being fucked by the effects of Climate Change while western countries are celebrating because "it's more sunny and warm now! :D", and "finally more viable real estate!"
Many of the issues CAN be and are linked to colonialism, reread what I wrote.
Yes, your points are pertinent and support problems that colonialism is relevant to, I did not claim otherwise.
However, you're clearly focused on negatives and crimes (in many cases rightfully so) the US has caused. But the question wasn't exclusive to the US and is not exclusive to the US.
For the OPs question, trying to exclusively link everything to or overstate the colonial influence is an example of what I was saying as well.
It's comforting to pretend that we just say one word "colonialism" and think that now we're experts on the subject. But there's so much more than colonialism, which again is a big factor (the first I listed), and overemphasis of it while disregarding the other real issues and nuances is counterproductive to learning.
Many of these issues can be also be related to the fact that the citizens of powerful countries are entitled assholes who vote their countries to continue the exploitation of other countries.
Your membership in one of those citizen groups is, of course, completely conjectural, but I have a strong opinion about it.
Colonialism has done really bad things in the African and Middle Eastern continent. When they withdrew they irresponsibly drew the borders and now civil wars happen all the fucking time
Yes, but OP was asking for more than a single high-level example. And, again, exclusively answering colonialism would be disingenuous if we implied that was THE answer instead of part of it.
I'm not convinced, considering the US and many other countries with high standard of living are also leading the world in external debt (both total and per capita).
Maybe you mean debt to GDP+wealth ratio? Or more specifically, bad credit with international banks.
I'm not an economist though, so I'd be curious to hear if there is more explanation for why you consider debt to be "the main reason."
I am aware that some countries have been "screwed over" by large banks that had specific detrimental stipulations for debt forgiveness though. For example, look at the Latin American Debt Crisis.
...the Fed convened an emergency meeting of central bankers from around the world to provide a bridge loan to Mexico. Fed officials also encouraged US banks to participate in a program to reschedule Mexico’s loans (Aggarwal 2000).
As the crisis spread beyond Mexico, the United States took the lead in organizing an “international lender of last resort,” a cooperative rescue effort among commercial banks, central banks, and the IMF. Under the program, commercial banks agreed to restructure the countries’ debt, and the IMF and other official agencies lent the LDCs sufficient funds to pay the interest, but not principal, on their loans. In return, the LDCs agreed to undertake structural reforms of their economies and to eliminate budget deficits. The hope was that these reforms would enable the LDCs to increase exports and generate the trade surpluses and dollars necessary to pay down their external debt (Devlin and Ffrench-Davis 1995).
Although this program averted an immediate crisis, it allowed the problem to fester. Instead of eliminating subsidies to state-owned enterprises, many LDC countries instead cut spending on infrastructure, health, and education, and froze wages or laid off state employees. The result was high unemployment, steep declines in per capita income, and stagnant or negative growth—hence the term the “lost decade” (Carrasco 1999).
Thought debt could go into some of the other categories. Calling it out individually or under a broader umbrella of economics would be fine, too. It's just a suggestion list for OP to research.