Shenyang F-6, Albanian and American Users

The Shenyang J-6/F-6 is the Chinese-built version of the Mikoyan-Gurevich MiG-19. The denomination of 'J-6' is used for those machines built and serving in China, while the denomination of 'F-6' is used for the exported machines. It has been exported to various countries, among them, the following ones:

• Albania: When Albania broke diplomatic relations with the USSR in 1962, the country went into a self-imposed political isolation with China being their only ally. Therefore, in 1965, after just six years of operations, the MiG-19PMs that operated with the 7594th Fighter Regiment were shipped to China (as China wanted to know about Soviet radar technology which they couldn't acquire firsthand) and were traded back for 12 new but radarless and cannon-armed Shenyang F-6 fighters.
  Eventually, 17 F-6s were delivered some of them being, according to some sources, the Shenyang F-6C version which has a braking parachute at the base of the rudder and the JJ-6/FT-6 version which is the two-seater trainer variant.
  Albania's relationship with China also deteriorated in 1978 and, hence, spares supplies were cut off. Facing the serious problem of a total unserviceability the Albanian Air Force had to start manufacturing vital airframe components and engine parts at the Aviation Maintenance Unit in Kucovë Air Base at Berat.
  According to Euromil, the Albanian Air Force had 24 Shenyang F-6 in service in as late as 1995. However, by early 2000s they were all written off except for the FT-6 trainers.
• United States of America: There is no evidence of any Shenyang F-6 flying with the United States Air Force. However, the US Aviation Museum had an unarmed F-6A (Shenyang's equivalent to the MiG-19P) with fake markings reminiscent of the People's Liberation Army Air Force at Chino, California.
  This aircraft was later repainted mimicking the Egyptian camouflage pattern and was given Egyptian markings and codes too. 

Sources:

1. https://en.wikipedia.org/wiki/Shenyang_J-6

2. Midland Publishing - Mikoyan-Gurevich MiG-19. The Soviet Union's First Production Supersonic Fighter

3. https://www.valka.cz/Sen-jang-J-6-kod-NATO-Farmer-t42341

4. Salamander Books - The Complete Book of Fighters

Aermacchi M.B.-326, Various users

The Aermacchi M.B.-326 is also used nowadays by the American National Test Pilot School. Most of them are ex-Impalas made by the South African Atlas. They are used by the National Test Pilot School located in the Mojave desert, in California.

Regarding the MB-326 in Paraguay, they were bought by the Paraguayan government in the early 1980s from Brazil. They were the Brazilian version, so, technically they were Xavantes. They were involved in many anti-drug operations during the 1990s, like, for instance, when on 6th December 1995 a small number of Xavantes departing from Punta del Este air base, attacked the narcotraffic air force by bombing their hidden camouflaged airfields in the region of Alto Paraná. They served until 2004 when they were replaced by the Embraer Tucano.

Sources:
1. https://en.wikipedia.org/wiki/Aermacchi_MB-326
2. http://www.ntps.edu/component/content/article/49/166
3. http://aeropinakes.com/wordpress/1995/12/06/xavantes-de-la-fuerza-aerea-paraguaya/ (translated)