Nepal security assessment
Nepal is a mess but you are safe
The world is a mess, Nepal is also, only currently more so. However, in summary: it is safe to trek and travel in Nepal, there may be strikes, delays and inconveniences—there may not—BUT you have never been a target. You are safe from orchestrated political violence, even Americans, so come have an adventure.
Personal safety
Theft from tourists is very rare and I feel secure travelling with expensive camera gear on our treks.
Kathmandu
Kathmandu is a city on the edge. The air pollution is disgustingly bad and dangerously unhealthy, #177 out of 178 capital cities, the rush hour traffic is to the point of virtual gridlock and the city can't even dispose of its rubbish satisfactorily. Despite these rather big issues, the historic old parts and the tourist ghetto of Thamel still have a chaotic charm.
Air safety
Nepal as only one main international airport (TIA; for a country of nearly 30 million), which is a complete mess with international flights mixing with 18 seater small planes and helicopters. Flights are frequently delayed and the terminals are overloaded. Hopefully, this might change with the opening of two new international airports in 2023.
The safety record of small plane flights is not particularly good, however conditions are incredibly challenging, and flying is still safer than road travel.
US travel advisory
The State Department has simplified their system, here is the Nepal travel advisory.
The future
The country has been in a slow motion death spiral for two decades and one would have hoped with the new constitution in September 2015, that the country might finally be climbing out of the abyss. However it has fallen further as ultimately the real problem are the greedy, narrow-minded geriatrics at the top of the heap who have yet to change their ways. Nepal will only truly make it to base camp once they are out of the way and there is a major change in the deeply, utterly corrupt political culture.
Currently the economy is kept alive by remittances from overseas (approximately 10% of the population is working overseas, literally millions of people) as industry is not developing . Inflation is running at around 7-15%; the unemployment rate is horrifying, and the list of serious flaws goes on. Administratively everything is held hostage by high level politicians despite a transition to a federal set up with seven provinces.
The problem is and always has been "the fox guarding the hen coop" with the politicians writing the rules to govern themselves, and they cannot even under pain of death see beyond their own pocket, beyond short term political gain. The country has been waiting in vain so far for the leaders to introduce universal law and order. Unfortunately the current crops of politicians are actually incapable of truly solving the current problems. Even the unbiased International Crisis group says the political parties "are badly run and ideologically impoverished organisations with few policy goals, unclear agendas and chronic leadership crises".
Expect occasional disturbances and strikes but normally these don't have too much effect on trekking plans.