The United States supplied arms to the new regime in Ukraine after the 2014 coup in Kyiv because it was in need of a fire in Central Europe. The Ukrainian regime set the needed fire by launching the war on the people of the Donbas region who rebelled against the Kyiv coup.
There are two scenarios of the US launching war against Russia. The first envisages a US military attack using all available means, including nuclear weapons. The second scenario envisages Russia’s economic isolation in order to induce a “change of political leadership”. The likelihood of combat action is quite real, as Washington may urgently need a “fairly large war”.
This claim involves speculation without evidence. It is a recurring pro-Kremlin disinformation narrative about Russophobia, US/NATO military aggression towards Russia, and alleged US funding of "colour revolutions" in Russia and other post-Soviet states. It also plays into the oft-used narrative that the West wants to conquer and subdue Russia, in order to portray Russia as the victim of unjustified aggression against which it must defend itself.
For similar cases about US and NATO warmongering towards Russia and its neighbours, see here.