There are no US nor NATO soldiers in Ukraine, there are Putin's Russia soldiers.
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It's a false statement that US soldiers are not involved in this conflict:
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Russia has put forward their conditions about how Ukraine would need to act to avoid being invaded. That, in my hood's called a threat, not a negotiation. Ukraine has decided not to be bullied.
In fact, Ukraine and Russia tried to negotiate among themselves. Have you read the text of the
Minsk agreements?
On top of that, the Donbas conflict could not exist without the support from Putin's Russia. War is expensive - who is funding the separatists? We all know who.
How much money Russia sent to the military needs of the separatists in the Donbas, and what sources do you refer to?
For example, judging by information from the official website of the
US Congress, America has been sponsoring the military economy of Ukraine for several years in the amount of more than $4 billion.

Even prior to the start of the war, Ukraine was a leading
recipient of U.S. military aid in Europe and Eurasia.
From 2014, when Russia first invaded Ukraine,
through March 2022, the United States has committed
more than $4 billion in State Department- and DOD-funded
security assistance "to help Ukraine preserve its territorial integrity, secure its
borders, and improve interoperability with NATO".
And this ''civilian war'' was started by Russia 8 years ago.
Are you sure you know the origins of the conflict?
In late 2013, Ukrainian President Yanukovych suspended negotiations with the EU in favor of strengthening relations with Russia.
After that, mass protests began in Kyiv.
In February 2014, Yanukovych was ousted from the presidency.
In April 2014, the residents of Donetsk and Lugansk declared their independence.
In response, Acting President in Ukraine Aleksandr Turchynov announced the start of an "anti-terrorist operation" in eastern Ukraine.
You can read a brief background of the conflict, at least in the
Britannica.
NATO or US soldiers are not involved as such (thanks to suchmoon for stating the obvious), some of them have left their countries to fight in Ukraine. In fact, some of them are now deserters in their
own countries because they left their countries' armies without permission.The Minsk agreements are effectively the type of bulling I refer to, pretty much the equivalent to signing a contract with a gun to your head. Including the second set that was signed of after Putin annexed Crimea.
No country likes to be forced into a unfavourable agreement - you could argue that since Germany had signed the peace agreements after WW I, they could not break them and would need to still be paying reparations of war. Those agreements are generally admitted as being one of the reasons for WW II and, in my view, the Minks Agreements are the basis for the current war.
Elaborating on that, you mention that the US has been sending funds to Ukraine. The US is of course interested in having closer links to Ukraine, but it is only thanks to Putin's policies that Ukraine has been pushed towards the west - and you cannot honestly blame them, there seems to be opportunity and development in that alliance, but certainly Ukraine has tasted Putin's cookies and they find them sour.
Putin is a Russian supremacist and, in general, Russia has historically seen Ukraine as the land they get the food from and burn and use so that the enemies supply lines are no longer sustainable. Can you blame Ukraine for wanting to try something different?
Re Donetsk and Luhansk, it is impossible to hold a serious referendum under such as strong funding and interference from Russia - with the internationally recognised guarantees, that could (at least IMHO) set a path for independence if that is the will of the people.
RE how much money has sent Russia to the separatist - I would like to return the question: how have the separatist fund their armed militias? War is expensive and the region is poor even for eastern standards, so ... who is to gain that would provide funds?
Anyway, I will give you some links, although I expect the usual "those sources are wrong" etc...
https://en.wikipedia.org/wiki/Russian_separatist_forces_in_DonbasIt is widely believed that the separatists are supported by the Russian Armed Forces.[13] Ukraine, the United States, and some analysts consider 1st and 2nd Army Corps to be Russian formations under the command of the 8th Combined Arms Army,[14][15][16][17] which was formed in 2017 in Novocherkassk, Rostov oblast. Although the Russian government often denies direct involvement, saying their soldiers were there voluntarily and not under orders, some of them have been captured with documents that said otherwise.
You can go to the Wikipedia references... plenty of evidence.