There are currently no imminent nuclear threats against the United States. However, there are events that are currently occurring that require closer monitoring. Let's see them below:
1) The United States and North Korea continue to face each other and the tension is increasing: On the part of the United States there are large numbers of men and material displaced towards the Korean peninsula.
On the part of North Korea that country continues advancing in its nuclear program.
2) The situation in the area is very volatile and tension can be aggravated at any time: the United States has deployed 100 F-16 fighter planes on South Korean soil with which it has been carrying out exercises in South Korean airspace on a regular basis during some time. Considering that such exercises often take place prior to an attack -as in the case of Operation Desert Storm- I can suppose a pre-emptive strike at any date against major strategic targets in North Korea, which could be carried out initially using F-35 and Tomahawk missiles. How would North Korea react? At best -that is, in the event that the US pre-emptive strike with the F-35s and Tomahawks knocks out North Korea's anti-aircraft defenses, the artillery pieces aimed at Korea South, and all its nuclear missile launchers- we could hope a quick and definitive solution to the South Korean problem. However, if the first attack does not achieve its objectives, South Korea's reaction may include attacks with weapons of mass destruction directed against any US allied territory that may be within its reach, especially South Korea and Japan. If it could also reach the bases of the United States in other areas of the Pacific and even attack the American continent, the situation would become unpredictable.
3) Another possibility that does not deserve to be dismissed in any way is that North Korea launches a first preventive attack against the United States, generating an electromagnetic pulse on its territory. That pulse would be generated by the detonation of a nuclear device housed in one or both of the two earth observation satellites KMS 3-2 and KMS-4 put into orbit by North Korea in April 2012 and February 2016 respectively. In that case, the negative consequences would be of all kinds: massive blackouts, total communications outages, destruction of electronic systems for airplanes, automobiles, trucks and trains, and all the ensuing chaos: Crashed planes, collapsed roads , Emergency services inoperative, etc.