Hi.
What consequences? Numerous but one of the most immediate is significant damage to satellites in the upper atmosphere, of which there are thousands. The commercial value of the satellites is high but you don't have to look upon it just in terms of dollars. Those satellites maintain key infrastructure like communications, GPS and gathering intelligence.
Overall, it is extremely unlikely that a country would want to create a significant detonation in the upper atmosphere, taking the damage from an incoming nuclear weapon could be less destructive to the country's infrastructure (and their capability to make a military response).
There is some details about the creation of artificial radiation belts in the atmosphere on this Wiki page: https://en.wikipedia.org/wiki/List_of_artificial_radiation_belts
As it explains there, charged particles tend to get trapped along magnetic field lines from planet earth. Various tests have been done already and there is hard data available. Many of those tests caused damage that rapidly resulted in the total failure of some key satellites (see the "Argus" and "Starfish" projects). There are now more satellites in space than ever before and they are an increasingly important part of the infrastructure.
In 2010, the United States Defense Threat Reduction Agency issued a report that had been written in support of the United States Commission to Assess the Threat to the United States from Electromagnetic Pulse Attack. The report, entitled "Collateral Damage to Satellites from an EMP Attack," discusses in great detail the historical events that caused artificial radiation belts and their effects on many satellites that were then in orbit. The same report also projects the effects of one or more present-day high-altitude nuclear explosions upon the formation of artificial radiation belts and the probable resulting effects on satellites that are currently in orbit
[extract from the Wikipedia article]
In summary: The US and most other countries are unlikely to detonate a significant nuclear device in the upper atmosphere to defend against incoming missiles. That could be helping the enemy cause more damage than they could cause on their own. The damage would not be limited to just US satellites, most satellites aren't completely geo-stationary, they move about and around the earth, so there would be damage to satellites globally.
Best Wishes.