I appreciate the input but something is amiss in your explanation.
This is how the TPY-2 X-Band Radar system functions:
Depending on the needs of the warfighter, the AN/TPY-2 radar can be deployed in two different modes. In forward-based mode, the radar is positioned near hostile territory, and acquires ballistic missiles in the boost (ascent) phase of flight, shortly after they are launched. It then tracks and discriminates the threat, and passes critical information required by decision makers to the Command and Control Battle Management network.
When the AN/TPY-2 radar is deployed in terminal mode, the radar’s job is to detect, acquire, track and discriminate ballistic missiles in the terminal (descent) phase of flight. The terminal-mode AN/TPY-2 also leads the Terminal High Altitude Area Defense ballistic missile defense system by guiding the THAAD missile to intercept a threat.
Source:
https://www.raytheon.com/capabilities/products/antpy2/
This radar system is effective in its mission in virtually any position and enables a (nearby) ballistic missile defense system such as THAAD to terminate an incoming ballistic missile during the
terminal phase of its flight (should the need arise).
You are assuming that US needs to install these radar systems across the world to get early warning coverage of ballistic and cruise missile launches from Iran and/or Russia which is plainly wrong. US receives such early warning coverage from a large number of assets positioned across the world in sea, land, air and space. Examples below.
Early warning from space (global coverage):
https://www.lockheedmartin.com/us/products/sbirs.html
http://www.airforce-technology.com/projects/space-based-infrared-system-sbirs/
https://foxtrotalpha.jalopnik.com/these-are-the-doomsday-satellites-that-detected-the-exp-1737434876
Early warning from oceans (global coverage):
https://foxtrotalpha.jalopnik.com/these-are-the-little-known-ships-that-make-missile-defe-1594677657
Early warning from air (global coverage):
http://www.afspc.af.mil/About-Us/Fa...26401/ballistic-missile-early-warning-system/
https://gizmodo.com/5989481/there-isnt-an-icbm-around-that-can-sneak-past-this-radar-array
http://www.afspc.af.mil/About-Us/Fact-Sheets/Article/249015/pave-paws-radar-system/
So my friend, AN/TPY-2 radar system is a goldfish in comparison to what US have stationed out there in regards to receive early warning of ballistic and cruise missile launches from any country. Not just the early warning, US have the capability to track the flight-path of a ballistic or cruise missile in real-time in any part of the world. Its surveillance network is of GLOBAL reach and proportions, and multi-layered.
Turkey wants to bolster its defenses against ballistic and cruise missiles for which US provided it an AN/TPY-2 radar system in 2012. Next step was to provide PAC-3 and/or THAAD systems to Turkey but this deal did not materialize due to political factors (and otherwise). Therefore, Turkey decided to acquire S-400 systems from Russia as an alternative. Now the problem is that S-400 systems cannot be hooked to the AN/TPY-2 radar system (or the US would not allow this). So if Turkey requests the US to remove its AN/TPY-2 radar system from its mainland, the latter shall oblige accordingly. But to assume that this move hampers American surveillance ability vis-a-vis Iran and/or Russia is sheer ignorance of how US surveillance system works and what kind of networks it comprises.