main difference between the late 90's and now is that, currently the tech companies are not offering anything innovating or life changing as similar to the internet. thats why valuations and dreaming about future tech are limited.
you need a similar type catalyst to have people dream delusionally about the future and accept high valuations. If something similar to the internet that has similar innovative patterns comes onto the scene, then sure tech bubble can get underway.
but valuations will be tame and range bound, thats why the market is dangerous.. since a large range bound market kills the breakout players.
take a look at the 1965 chart, I use to think we were similar to 95, but I don't see anything revolutionary happening within the next few years. The biggest mental shift has been 70's style inflation acceptance.
russia is even more dangerous, since they were able to convince the rest of the world that the dissolution of the USSR was going to lead to golden times. The dissolution could have as well been a plan to modernize their forces using a capitalistic model. You are seeing wisps of it now, with Russia pulling out of arms treaty regarding troop deployment on the borders with Europe. With Petro dollar wealth, and Russian technology prowess. The greatest threat to USA is still Russia.