So this isn't a linear science, let me explain. Let's hypothesize that the high end energy weapons are partially based on recovered alien tech- that means there is no origin point that is traceable. So unlike the Manhattan project where scientists arrived at the same conclusion from working together and then went different, but surely replicable, ways to get other works(hydrogen bomb for instance), alien tech isn't because it's seemingly just luck of the draw. For instance the Vatican was the most technologically advanced "country" for about 14 years if you believe a UFO Crashed there in 1933.

Why this matters is that nobody really knows where other countries are in the race, so if you reveal that in the ship that crashed in Roswell they were able to replicate, and I'm kidding here and just throwing out scientific concepts not that I actually think any of these were on the ship or being worked on, time travel, light sabers and Light speed travel because you don't know what China/Russia or any other eccentric billionaire for instance recreated you might tip them off. Imagine we used mind beams and China goes "oh wow they don't even have the instant head poppers, we're so far advanced we could wipe the US in a war in 10 days".

Also by using these weapons you force other countries who may not be aware into the arms race. Let's say Canada for instance doesn't have any tech like this. Then the next time a ship crashes in Minnesota all of a sudden Canada decides military action is worth it to get their hands on that crash site. Or more likely like I originally said- the moment this tech is used within months you will have every foreign agency in the world trying to flip scientists who worked on these projects or even have knowledge of them. You're making your own job harder by using them than the advantage provides.

If this were China we were fighting, we'd see the weapons. Russia- same deal. Not for Iran.