That’s the way. Give over the production of our weaponry and tech to the enemy so that it can be studied and copied and countered and cut off when it is time to hit America.
The Russian rockets engines aren’t our tech. Also, they’re selling *US* their rocket engines because our companies are having problems making engines as good - their liquid fueled disposable engines are actually better and more reliable than ours, in general, with the exception of SpaceX and maybe Blue Origin’s engines at current.
The U.S. has been using the RD180 series engines on our rockets for over 20 years. In 2014 work was begun on a U.S. replacement and now 7 years later none has been produced.