There are guys who may be involved in training and/or maintenance, in addition to liaison officers, etc.. Pretty common to have small numbers of U.S. personnel in any friendly country of significance. But there is a difference between those staff-type positions, and actual combat troops. That is a distinction that is generally considered a given when defense people are talking about this stuff.
That’s right 50,000 plus of those advisers died in Viet Nam
There has been a long term training relationship between the U.S. and the Ukraine. This is similar to relationships we have with dozens of countries. Most often we do mutual training through the National Guard State Partnership Program.
Under this program, a State will routinely, 1-3 times a year, send Army or Air National Guard units, generally company size (100-150 troops) or smaller to the same partner country. It’s a low-cost way to provide training for the Guard, and the Guard units get information about other countries as they train with their soldiers and airmen.
The units may be combat units, but the mission is strictly training.