Conspiracy theory; no evidence given. This narrative falls within the broader pro-Kremlin disinformation efforts attempting to deny the existence of genuine grass-roots protests, portraying them as foreign-led efforts and fake colour revolutions.
This is also part of a disinformation narrative about US-led regime change operations against left-wing governments in Latin America. You can see other examples of this narrative in the EUvsdisinfo database, such as the alleged presence of a US marine in the Venezuelan barricades and the promotion of a Ukraine-style 'colour revolution', the training of Venezuelan exiles in Guyana for military operations inside the country, preparations for a military intervention after forcing Brazil to join NATO, deliberate blackouts in South America caused by the US, or the existence of plans for the secession of oil-rich regions in both Venezuela and Mexico.
Although the United States "applauds the Bolivian people for demanding freedom", there is no evidence to suggest that the US was directly involved in Evo Morales' resignation.
Morales’ resignation came during mass protests in the country after the Organisation of American States (OAS) reported “extensive irregularities” in the election for his fourth term. Morales had invited the OAS to observe the vote, and the group called for the election to be annulled. Read the full debunk by Polygraph.
Read the statement from the EU's High Representative/Vice President Federica Mogherini on the situation in Bolivia here.
For further cases on the situation in Bolivia, see here.